and getting ePSXe to kick off could be objectively the simplest of the two.

Open Retroarch -> select the game's cue or m3u -> play vs Open ePSXe -> configure sound plugin -> configure input plugin -> configure graphics plugin -> configure drive plugin -> select the game's cue, bin, etc -> play (and when you change the game for another one pray for the settings you had working OK to still do)

And still you say it's easier on ePSXe, I don't get it.

Just like ~70% of them uses NVIDIA overwhelmingly with proprietary and closed software.

Yes, because the Nvidia driver is a lot better than the open source driver. This is not the same case at all. In fact, Mednafen is objectively better than ePSXe. Also, if the Nvidia driver was open sourced all the community would benefit from it. This is exactly what the ePSXe devs are doing wrong too, but they are not a multi million dollar company, they are only some selfish individuals that made the entire PSX emulation stagnant for a lot of years instead of helping the community for... fame? I guess.

Dolphin is where it is right now because they open sourced their code, gaining more contributors that fix specific problems that other devs couldn't. MAME not so long ago merged the MAME and MESS projects into one and the majority of devs say that is the best thing that happened to the project. Being so old and big project imagine where it would be right now if it was closed-source. Probably abandoned and the emulation (and preservation) of arcade and other systems would be crap. The same with GameCube and Wii emulation. And that's exactly what happened for a lot of years with Playstation emulation.

So no, RetroArch and all the devs that contribute to the project (with their emulators or the ones that work on RA itself) is the best thing that happened to the emulation world, because making the project open source they are ensuring that the preservation of software is a thing even if every dev dies tomorrow.