CORBA never scaled to the level that Uber needs to. Pre-pandemic, you’re talking hundreds of thousands to millions of requests per second globally. Also you never saw a CORBA project with thousands of engineers checking in code multiple times a day. All these are factors too.

People on HN always think “all it’s doing is matching a rider with a driver, why is it so complicated? I can write it in a weekend!” Sure, but it won’t scale.