If Vim isn’t responsive in a machine with hundreds of MHz something is very wrong with your setup. Vim was fast on machines with dozens of MHz. Either a bad terminal emulator or some plugin making it slow, I’d guess.
User problem: since I use Vim for everything, my expectations as far as responsiveness goes are probably not calibrated correctly. It is almost always very good, so the moments of badness are noticeable. The user (me) is unreasonably picky.
Technical: LaTeX syntax highlighting. It is I’m pretty sure, generally known to be a bit of a pain. Lots of nested environments that can go back dozens of lines and change how commands are interpreted. It is happy in a decent (not huge or anything) sized Fortran code, so I think config is mostly OK. Maybe I should look around and see if there’s a nice LaTeX plugin out there.
You have every right to have high expectations for performance with Vim
Depending on how hard you push it, Neovim can also be noticeably faster than Vim (notably Lua/LuaJIT being much faster than VimScript)
Furthermore there's the whole intentional delay on ESC exit from modes like an aborted search query... that can make it feel unresponsive but it's just a timeout. Try it, hit '/' in vim, then ESC to abort the search, count a full second of unresponsiveness.
This blog speaks to such ESC delays one encounters in vim:
However we have many more layers now. I had a 80x24 serial tty exchanging ASCII characters with the computer back then.
According to https://vt100.net/heath/z19-om.pdf it can do 110 to 9600 baud. It was connected to some Z8000 based Onyx server. It was generally good but incredibly slow when more than four or five of us were compiling code for the tests at university class. Pascal, Berkeley p system or something with a similar name.