How is it sad? Everyone is learning how to build a better game engine. Are you suggesting that the same pull requests should have been made against an open source game engine? No open source game engine comes close to UE4 in feature set.
That people are contributing free work for someone else (Epic) to make money off of. Yes, I think they're suggesting to put that effort towards an open source engine, or towards a company that will reward you in some way for doing said work.