Sites at that scale that cannot afford errors, downtime, or system breaches operate massive IT teams just to keep the systems running. That’s before even touching Logistics,Advertising, customer service, seller outreach, brand management, human resources, etc, etc. Ebay in 2023 had 132 Million customers. That’s 12,000 customers per employee per year, or 32 customers per employee per day assuming they worked the full 365 solid. A rather lean storefront actually, probably propped up significantly by the labor of their third-party sellers.
I don’t personally disagree, but I don’t know what sort of business challenges they face. Also I should add that 132 Million number isn’t traffic or transactions, that’s verified customers that have made at least 1 purchase. That all being said there is definitely a redesign/restructure/rebase needed, but the ship takes crew to keep it sailing even if it needs remodeled/repaired/etc.