`open -a NameOfAppYouWantToUse fileyouWantToOpen.foo` will reliably open a file with whichever app you want. Just `open path/to/directory` will open a Finder window to that directory. The file open dialog in macOS also exists and works just fine. You can drag file icons from GUI apps into terminal windows to insert their absolute path. You can drag files from Finder onto an app icon to open-with that app.
Transitioning between terminal workflow and GUI workflow feels better to me on macOS than either Linux or Windows; although with Listary Windows is decent.
I constantly use iTerm (or even just the regular MacOS Terminal).
It's easy to have it take up the whole screen and the most "MacOS UI" I'll ever see is the title bar for the window, which yeah can be ugly to look at but really isn't something that keeps me from working or anything.
I guess IDE's use a ton of UI, but I wouldn't say that's MacOS cruft on its own.
The only time that I have to interact with the UI is when I have to do something on System Settings, which is also dreadful.
The most complicated thing I do in Finder is browsing pictures and installing an Application, both of which is does a perfectly fine job at.
I live exclusively in terminal or browser, all other apps are opened via terminal and closed with cmd+q.
I like macOS because it doesn't get in the way even when I almost never had to interact with Finder (which I still find weird every time I had to use it, for web uploads etc).