I’ve designed, built, and maintained some pretty complex marketplace sites that get that much traffic and have a bunch of independent people dependent on its uptime for income. I can empathize with the “if it ain’t broke, don’t fit it” philosophy.
That said, eBay smells like it has grown into one of those large companies that require 85 meetings to get anything done. I look at that site and wonder what the hell is going on in that org. Their ratio of people to tech debt just feels off to me.
That company has felt like it was poorly run for a long time now. They’ve been coasting on inertia.