That has once been true for Unity as well. People laughed about it being for gimmicky games that weren't too serious.

I think an engine today is about a lot more than rendering performance and quality. It is about the development pipeline, the tools it comes with and the interfaces to integrate assets and loading those. In that regard Unity offers a lot by now.

They also feature their asset store and whatnot. Of course it will take some time to develop such features for any new engine and it won't come to pass until it reaches a critical mass.