I mean yeah War_Hero, you silly game developer (ha who even heard of Halo) and ex Toribash dev in particular, wave off your low expectations!
Jokes aside, can't really speak for hampa on engine choice and other stuff as tbn is still mainly being developed by him alone, but one of reasons to choose Unity over physics-focused game engines was that it allows super simple porting to other platforms. Current Toribash code is also pretty convoluted, so doing a complete overhaul instead of trying to refactor it imo is a good way to go about the new game (e.g. now when we have to do some minimal updates Dranix can sometimes spend more time trying to make everything not fall apart than he would on just adding new stuff - and exact same thing applies to game server).
There obviously are other engines with similar possibilities as of Unity's (and also have full C++ support), but you'd need to ask hampa why he went with it specifically. But yeah, it's much better than what we use now anyway - especially when you consider character/environment customization possibilities.