Change permisions on /usr and /usr/local to link Homebrew package

How does one change permissions for /usr or /usr/local? I tried doing sudo chmod 775 /usr/local, but it says

chmod: Unable to change file mode on /usr/local: Operation not permitted`

so I ran ls -l /usr and it showed

drwxr-xr-x   17 root  wheel    544 Nov 20 14:08 local

(it also showed the stuff for the other things in there, but those are irrelevant). Also, why do I have to use sudo, as I have admin privileges, shouldn't that be enough?

I am trying to change the permissions so that I can install simple2d using Homebrew. When I run brew link simple2d, it says that it can't symlink into /usr/local/Frameworks, but Frameworks doesn't exist, so I tried to create it, and it won't let me because of permissions.

I am using macOS Mojave. On a mac that has System Integrity Protection

When I run brew doctor it outputs

Please note that these warnings are just used to help the Homebrew maintainers
with debugging if you file an issue. If everything you use Homebrew for is
working fine: please don't worry or file an issue; just ignore this. Thanks!

Warning: "config" scripts exist outside your system or Homebrew directories.
`./configure` scripts often look for *-config scripts to determine if
software packages are installed, and what additional flags to use when
compiling and linking.

Having additional scripts in your path can confuse software installed via
Homebrew if the config script overrides a system or Homebrew provided
script of the same name. We found the following "config" scripts:
  /Library/Frameworks/Python.framework/Versions/3.7/bin/python3.7-config
  /Library/Frameworks/Python.framework/Versions/3.7/bin/python3.7m-config
  /Library/Frameworks/Python.framework/Versions/3.7/bin/python3-config

Warning: You have MacPorts or Fink installed:
  /opt/local/bin/port

This can cause trouble. You don't have to uninstall them, but you may want to
temporarily move them out of the way, e.g.

  sudo mv /opt/local ~/macports

Warning: Unbrewed header files were found in /usr/local/include.
If you didn't put them there on purpose they could cause problems when
building Homebrew formulae, and may need to be deleted.

Unexpected header files:
  /usr/local/include/lauxlib.h
  /usr/local/include/lua.h
  /usr/local/include/luaconf.h
  /usr/local/include/lualib.h
  /usr/local/include/node/android-ifaddrs.h
  /usr/local/include/node/ares.h
  /usr/local/include/node/ares_build.h
  /usr/local/include/node/ares_rules.h
  /usr/local/include/node/ares_version.h
  /usr/local/include/node/libplatform/libplatform.h
  /usr/local/include/node/libplatform/v8-tracing.h
  /usr/local/include/node/nameser.h
  /usr/local/include/node/node.h
  /usr/local/include/node/node_buffer.h
  /usr/local/include/node/node_object_wrap.h
  /usr/local/include/node/node_version.h
  /usr/local/include/node/openssl/aes.h
  /usr/local/include/node/openssl/archs/BSD-x86/opensslconf.h
  /usr/local/include/node/openssl/archs/BSD-x86_64/opensslconf.h
  /usr/local/include/node/openssl/archs/VC-WIN32/opensslconf.h
  /usr/local/include/node/openssl/archs/VC-WIN64A/opensslconf.h
  /usr/local/include/node/openssl/archs/aix-gcc/opensslconf.h
  /usr/local/include/node/openssl/archs/aix64-gcc/opensslconf.h
  /usr/local/include/node/openssl/archs/darwin-i386-cc/opensslconf.h
  /usr/local/include/node/openssl/archs/darwin64-x86_64-cc/opensslconf.h
  /usr/local/include/node/openssl/archs/linux-aarch64/opensslconf.h
  /usr/local/include/node/openssl/archs/linux-armv4/opensslconf.h
  /usr/local/include/node/openssl/archs/linux-elf/opensslconf.h
  /usr/local/include/node/openssl/archs/linux-ppc/opensslconf.h
  /usr/local/include/node/openssl/archs/linux-ppc64/opensslconf.h
  /usr/local/include/node/openssl/archs/linux-x32/opensslconf.h
  /usr/local/include/node/openssl/archs/linux-x86_64/opensslconf.h
  /usr/local/include/node/openssl/archs/linux32-s390x/opensslconf.h
  /usr/local/include/node/openssl/archs/linux64-s390x/opensslconf.h
  /usr/local/include/node/openssl/archs/solaris-x86-gcc/opensslconf.h
  /usr/local/include/node/openssl/archs/solaris64-x86_64-gcc/opensslconf.h
  /usr/local/include/node/openssl/asn1.h
  /usr/local/include/node/openssl/asn1_mac.h
  /usr/local/include/node/openssl/asn1t.h
  /usr/local/include/node/openssl/bio.h
  /usr/local/include/node/openssl/blowfish.h
  /usr/local/include/node/openssl/bn.h
  /usr/local/include/node/openssl/buffer.h
  /usr/local/include/node/openssl/camellia.h
  /usr/local/include/node/openssl/cast.h
  /usr/local/include/node/openssl/cmac.h
  /usr/local/include/node/openssl/cms.h
  /usr/local/include/node/openssl/comp.h
  /usr/local/include/node/openssl/conf.h
  /usr/local/include/node/openssl/conf_api.h
  /usr/local/include/node/openssl/crypto.h
  /usr/local/include/node/openssl/des.h
  /usr/local/include/node/openssl/des_old.h
  /usr/local/include/node/openssl/dh.h
  /usr/local/include/node/openssl/dsa.h
  /usr/local/include/node/openssl/dso.h
  /usr/local/include/node/openssl/dtls1.h
  /usr/local/include/node/openssl/e_os2.h
  /usr/local/include/node/openssl/ebcdic.h
  /usr/local/include/node/openssl/ec.h
  /usr/local/include/node/openssl/ecdh.h
  /usr/local/include/node/openssl/ecdsa.h
  /usr/local/include/node/openssl/engine.h
  /usr/local/include/node/openssl/err.h
  /usr/local/include/node/openssl/evp.h
  /usr/local/include/node/openssl/hmac.h
  /usr/local/include/node/openssl/idea.h
  /usr/local/include/node/openssl/krb5_asn.h
  /usr/local/include/node/openssl/kssl.h
  /usr/local/include/node/openssl/lhash.h
  /usr/local/include/node/openssl/md4.h
  /usr/local/include/node/openssl/md5.h
  /usr/local/include/node/openssl/mdc2.h
  /usr/local/include/node/openssl/modes.h
  /usr/local/include/node/openssl/obj_mac.h
  /usr/local/include/node/openssl/objects.h
  /usr/local/include/node/openssl/ocsp.h
  /usr/local/include/node/openssl/opensslconf.h
  /usr/local/include/node/openssl/opensslv.h
  /usr/local/include/node/openssl/ossl_typ.h
  /usr/local/include/node/openssl/pem.h
  /usr/local/include/node/openssl/pem2.h
  /usr/local/include/node/openssl/pkcs12.h
  /usr/local/include/node/openssl/pkcs7.h
  /usr/local/include/node/openssl/pqueue.h
  /usr/local/include/node/openssl/rand.h
  /usr/local/include/node/openssl/rc2.h
  /usr/local/include/node/openssl/rc4.h
  /usr/local/include/node/openssl/ripemd.h
  /usr/local/include/node/openssl/rsa.h
  /usr/local/include/node/openssl/safestack.h
  /usr/local/include/node/openssl/seed.h
  /usr/local/include/node/openssl/sha.h
  /usr/local/include/node/openssl/srp.h
  /usr/local/include/node/openssl/srtp.h
  /usr/local/include/node/openssl/ssl.h
  /usr/local/include/node/openssl/ssl2.h
  /usr/local/include/node/openssl/ssl23.h
  /usr/local/include/node/openssl/ssl3.h
  /usr/local/include/node/openssl/stack.h
  /usr/local/include/node/openssl/symhacks.h
  /usr/local/include/node/openssl/tls1.h
  /usr/local/include/node/openssl/ts.h
  /usr/local/include/node/openssl/txt_db.h
  /usr/local/include/node/openssl/ui.h
  /usr/local/include/node/openssl/ui_compat.h
  /usr/local/include/node/openssl/whrlpool.h
  /usr/local/include/node/openssl/x509.h
  /usr/local/include/node/openssl/x509_vfy.h
  /usr/local/include/node/openssl/x509v3.h
  /usr/local/include/node/pthread-barrier.h
  /usr/local/include/node/stdint-msvc2008.h
  /usr/local/include/node/tree.h
  /usr/local/include/node/uv-aix.h
  /usr/local/include/node/uv-bsd.h
  /usr/local/include/node/uv-darwin.h
  /usr/local/include/node/uv-errno.h
  /usr/local/include/node/uv-linux.h
  /usr/local/include/node/uv-os390.h
  /usr/local/include/node/uv-sunos.h
  /usr/local/include/node/uv-threadpool.h
  /usr/local/include/node/uv-unix.h
  /usr/local/include/node/uv-version.h
  /usr/local/include/node/uv-win.h
  /usr/local/include/node/uv.h
  /usr/local/include/node/v8-debug.h
  /usr/local/include/node/v8-experimental.h
  /usr/local/include/node/v8-inspector-protocol.h
  /usr/local/include/node/v8-inspector.h
  /usr/local/include/node/v8-platform.h
  /usr/local/include/node/v8-profiler.h
  /usr/local/include/node/v8-testing.h
  /usr/local/include/node/v8-util.h
  /usr/local/include/node/v8-version.h
  /usr/local/include/node/v8.h
  /usr/local/include/node/v8config.h
  /usr/local/include/node/zconf.h
  /usr/local/include/node/zlib.h

Warning: Unbrewed static libraries were found in /usr/local/lib.
If you didn't put them there on purpose they could cause problems when
building Homebrew formulae, and may need to be deleted.

Unexpected static libraries:
  /usr/local/lib/liblua.a

Warning: You have unlinked kegs in your Cellar
Leaving kegs unlinked can lead to build-trouble and cause brews that depend on
those kegs to fail to run properly once built. Run `brew link` on these:
  python@2
  python
  nano
  lua
  hamlib
  simple2d