Everyone telling you that it's fast because iTerm2 is slow. Terminal.app is already faster than iTerm2 and on par o very close to most other alternatives in terms of speed.

I also used Terminal until recently and don't use any of the advanced features alternatives provide. The main reason to switch from Terminal.app is truecolor support. The terminfo thing is annoying but I just setenv TERM in ssh config. Better split panes is nice. Configuration in a text file is a matter of taste, but documentation is good.