I hope Buck2 is better. Like I said, I have no experience with it.

My issue is more organizational. Meta, as a company, in my experience, does not put in sufficient investment to build a mature, robust open source project with few exceptions. Even things like the www test infra, which are core to the company when I was there had ~1 FTE SWE. That's not open source but you get my point. Buck (and Thrift) seem to have been woefully underinvested for years. Thrift was originally an intern project at a time when Stubby (Google's protobuf-based RPC) was not open source.