You can still install just python3 and call that as-is if you are not using any extra libraries.
If you are using any extra libraries, you should not be installing that system-wide, and should use an environment anyway.
You literally can still use python3 for simple scripting tasks on your Mac, hell I do everyday. One just has to install python3, a trivial task on a Mac.
homebrew will install pip3 along with python3; on my install, python3 packages go in /usr/local/lib/python3.6/site-packages while python (2.7) packages go in /usr/local/lib/python2.7/site-packages . I can't understand the complaint except for having to type 3 I guess?
If you are using any extra libraries, you should not be installing that system-wide, and should use an environment anyway.
You literally can still use python3 for simple scripting tasks on your Mac, hell I do everyday. One just has to install python3, a trivial task on a Mac.