mastering movement (which is core to speedrunning) is very fun in many games.
example, half life. Half life speedrun is both a nostalgia blast and an impressive display of skill, and strafe/gauss jumping is FUN
TAS are pretty fun to watch too, breaking a game very core to achieve "a perfect run" has some unexpected depth (especially the tas that fuck with game memory are crazy cool to me)
I will admit, I dont see the appeal in a game like goldeneye. but whatever. everything is ultimately meaningless, if you have fun doing it (or streaming it), who cares