brew is an amazing achievement. It doesn't do random unwanted updates at odd times. It doesn't do anything at all unless you run run it. And it tells you want it will do beforehand. Nobody would have "filled the void" - building software isn't a zero sum game. If someone had something better they would have continued to work on it and it would have "taken over". There, I said it.
That is incorrect. Brew will do random upgrades when running `brew install` unless you set the non-default `HOMEBREW_NO_AUTO_UPDATE=1` [1] so every now and then when you brew install something it will e.g. upgrade the python binary from 3.x => 3.(x+1) and break all virtualenvs using symlinks.
Python is just one example, I've spend countless time fixing random broken packages due to the unpredictability of `brew install`.
This is just a misunderstanding of how brew works. Brew is doing what it is designed to do. Your assumptions are that brew should be able to "pin" a package to an exact version, or that it is selecting packages at random to upgrade, but those assumptions are wrong.
However brew does support your use case, but it take some extra effort. If you want to use brew to install an exact version of python you need to create a tap: https://docs.brew.sh/How-to-Create-and-Maintain-a-Tap
Also, you aren't forced to use brew to install that version of python. You can do so yourself using the standard make; make install. It would be best to install it under /opt. Or use any other available method of installing software on your mac.
