I've been around, there's the technic launcher, ATLauncher (that one was the go to for making packa for playing with friends), the FTB launcher, as mentioned the curseforge launcher was part of the twitch app for a while (I think it was also something like the Curse app before that?), and then Prism Launcher is actually a fork of a fork of MultiMC, but the in-between fork was a little bit of a controversial mess that fell to a hostile takeover by one of the maintainers - which spurred the remaining maintainers to make what I see as the best launcher currently available. Oh, and I think modrinth might have a launcher now?

Oh, yeah, I also remember the old Minecraft launcher, I think there was a modded version of that with support for multiple profiles so you didn't have to switch mods manually!

It's funny how much history there is if you go digging into things like this, and I'm sure I missed a lot.