You can do whatever you want if you are a power user, the tools are there to get around Gatekeeper.

For everyone else it's probably sane to have it, works as a decent filter so someone not tech-savvy don't get hurt by installing malware disguised as an app, one would just need to state incredible features that almost any normal user would like to have, and make them click to install. Gatekeeper diminishes that risk by a lot unless you learn how to bypass it, which requires you having decent skills and probably wouldn't fall for the bullshit that malware apps try to bait people with.

I really don't understand what the issue is? Gatekeeper is merely a warning that introduces a minimal friction if what are you trying to run is created by an entity that chose not to present itself. It only happens once per application, not per launch. I've spent more time reading this thread than I have removing quarantine flags in the last five years.

Apple has a lot to be criticized for but gatekeeper (and SIP) isn't that.

So that you don't accidentally run malware. MacOS is not iOS, you can run unsigned code if you really want to, but it will make you jump through a few hoops.

I want to be a power user on my Mac, I don’t want my mom’s Mac to function like my devbox.

People like and need the apple sandbox. Others need an unlocked *nix machines