I do not see why not, people were thinking like that 20 years ago, it isn't like your 3D engine will have to implement all techniques from the last 50-60 years

I do not see why not, people were thinking like that 20 years ago, it isn't like your 3D engine will have to implement all techniques from the last 50-60 years (no need for wolf3d raycasting, for example and a lot of the shading and lighting code will become simplified once everything is capable of raytracing). Also AFAIK UE5 contains something like 5 render paths for different rendering approaches for all the different hardware and game types they need to cater to, but a specialized engine wont need to be that generic.