I use Emacs 29 RC with JIT compilation. Seldom any difference at all.
Granted I use a Doom derivative that shows a popup where you see command auto-completion but in 2023 this is absolutely inexcusable, if not laughable.
If it can't work reasonably well out of the box then it is a failure.
I'm already eating down votes in another comment which ironically only cements my decision to move away from Emacs.
> If it can't work reasonably well out of the box then it is a failure.
It is not out of the box though, is it? It sounds like the code that shows you the popup might not ship with stock Emacs.
Do you get the lag if you start Emacs with `emacs -Q`? Do you get it with Doom proper?
Can't promise I'll try again ever. I tinkered a good amount and lost faith. Nothing should need that much time and effort spent to have basic stuff working acceptably.
I think people easily lose perspective. It's OK to love what you do and play with it but people swing too far in that direction and forget that others actually use their stuff and need to get work done with it.