> Also we are talking here about Emacs "distributions" (Spacemacs, Doom Emacs) which come with a lot of code, and ELisp is not particularly fast.

I've just tried Doom Emacs on 27.1, with the default stuff plus some minor additions, and it starts within 900 ms on my laptop (Intel(R) Core(TM) i7-9850H CPU @ 2.60GHz).