All of the major engines are written in C++. I've tried Unreal, Unity and Godot. They all have their flaws. With Unreal and Godot those flaws are mainly the scripting languages BP and GDScript which one can get tired of quite easily, especially BP. You can of course use C++ for all your scripting but both engines strongly encourage you to use their scripting solution for a big chunk of your game. (Unity has a bunch of other issues and isn't source available, although C# is fairly pleasant to work with IMO).
There is definitely need for an OOP engine in Rust just as there is need for an ECS engine in Rust.
Is there a need for an OOP engine in Rust?
I don't want to be too negative here — the developer of Fyrox seems like an incredibly talented and productive engineer and they can work on whatever they please, more options in the ecosystem is always a net good — but in my experience attempting to model OOP patterns in Rust is almost always the wrong decision.
And bevy isn't taking what's good from different engines? Bevy gets inspiration from everywhere. Just because it uses an ECS doesn't mean it's all developed in a bubble.
OOP in fyrox means composition and message passing.