> I don't use Mac but what's wrong with the default?
Nothing, it works great. As someone who tried a bunch of alternatives: sorry but it's a waste of time unless you look at the long list of iterm2 features (terminal.app has many of them anyway) and think you might use those often (I don't, quite happy with my other apps covering for most of the features missing from the terminal.app): https://iterm2.com/features.html
Complete I would say. However Mac uses GNU software from around 2006, since around that time a lot of GNU software switched from GPLv2 to GPLv3.
That means Mac ships GNU screen version 4 from 2006, while latest version is 5.
I try out the new apps each year and always go back to Terminal.app. My one gripe with it was that Opt-Del didn't delete words, which I learned last year can be fixed by Preferences > Profiles > Keyboard > Use Option as Meta key
> GNU Screen seems to be stagnant
Is it stagnant or mostly complete?