Gentoo is more about the fun of building a Linux distro that is perfectly tailored to your hardware and personal preferences. Sometimes you’ll see a performance increase of 0.01%, sometimes 25%+. Just depends on a lot of different things.

The build times are really only a consideration on first or second install of the OS. And even with your first install, you’ll probably want to start with the pre-built options, and then gradually move away from that to compiling more and more of your own system.

There are a couple apps like Firefox that also have pre-compiled binaries available for Gentoo, so no waiting there. Of course, there’s also Flatpak for desktop-based apps.

Otherwise, you just compile what you want, when you want. And you can tell Portage how much in terms of cores/threads/resources it gets to use when compiling, so that it can just run in the background while you’re doing your normal thing (or scheduled for when You’re not using your machine).

Portage is also a phenomenal package manager, and can track and satisfy all dependencies for you as-needed. You can also specify what elements of your system to keep on stable, vs testing, etc. It’s not like Slackware.

Gentoo is what was used to build ChromeOS, along with many other distros. It’s as complex/simple, secure/insecure, private/un-private, latest-and-greatest/LTS as you tell it to be. You can choose to update things continuously in the background, or just once a week overnight, or on any other schedule that you want.

You’ll probably learn some new things in the course of installing it, but follow the handbook to the letter, avail yourself of the community, and be patient to start with. It works for me, and I like it, but there are plenty of excellent pre-cooked distros that are also great. I’m just a tinkerer by nature, and enjoy getting increasingly more out of my machines over time.