An athlete background would have been really cool, yeah
Shit why didn't we think of it?
Well there's always workshopping as the game goes along... Though I would had though Leader background would fit for the athlete background as well. Something like Captain maybe? After all people look up a lot to those in sports and a big part of team games is knowing when and how to follow and when to lead.
The thing about the speedrunner background though. It's the most achingly human and modern of the paths. Here you/the player is flailing about socially and physically. Seen in a lowly light and causing wincing to other people you interact with. You have existences a lot older, gotten themselves together better or more refined than you wincing and considering you lower than human or just have bad taste. And yet (hopefully) you're doing your best, muddling through life like every other average joe. Meeting and bonding with Asterion seems more like a blessing to you the player. Somebody who has been degraded to be less than human all their life and afterlife finds somebody with similar enough circumstance and chooses as a person to bond with them.
Even as everybody involved cringes. Honestly I'm waiting for like even the narration to dunk on the Speedrunner master.