Not to forget the fact that even though UE4 does have more features than Unity. UE4 ain’t complete.
I don’t know this for a fact, but it seems to me that many issues that ARK: Survival Evolves has, is not because the game devs, but because of UE4. I’m referring to the performance problems with the ARK game.
Also, ins’t UE4 only two years old? Because for that short time, actually there already many AAA and indies that use this engine. Like ARK, Flames in the Flood, EVERSPACE. And AAA game the Street Fighter thing.