Warhorse Studios have been created 14 years ago and they only made the 2 KCD games.
Arrowhead Game Studios, their 2 last games are Helldivers 1 and 2, Helldivers 1 is from 2015.
Kingdom Come Deliverance 2 and Helldivers 2 don’t have good performances because they use a “better optimised engine than Unreal”, it’s because these 2 games were developed and optimised for near a decade.
CryEngine last update was May 19, 2022.
Stingray has been discontinued in 2018.
Furthermore, KCD’s graphics are not that impressive, it is the artistic direction that carry the game’s graphics. Visually it’s equivalent to the medium settings of top AAA games, not more.
But both games make perfect use of older technologies.
To finish, Valorant has been updated to UE 5.3 (the game was on UE 4) and guess what, it’s running slightly faster at 900+ fps at 1080p, not slower. Moreover the game now takes 24GB instead of 58GB.
And don’t get me started on the tools and the documentation to build a game in CryEngine it would require to literally multiply the time necessary to make the same game than in UE with no better performances.