I'm not sure how to feel about it honestly.

I personally think that it's fine. There are bound to be casinos which look a bit like each other due to having the same provider behind their UI design and whatnot, and that is totally okay. It is more cost effective to operate that way for most casinos and as long as they pass on these savings in the form of lower house edge to players, I don't see any issues.

But there are also carbon copy sites of each other that would probably each benefit from some sort of a makeover.