I'm programming an open-world sandbox game but I need some sort of good game engine. I need a game engine that can support a lot of blocks 3D models, and also handle animations and meanwhile add HD graphics. Most of my textures are 32x32, but water, sky, and more are higher. I only have a team of a handful (TBH, I have 3) programmers with some experience.
There aren't any engines that are really optimized for an open-world game. That said, it's probably going to be easier to use an existing engine rather than, for example, rewriting model-and-animation file loading code.
Every engine you've mentioned has been used for open world games in the past.
Well, Unity does have LoadLevelAdditiveAsyc which is a foundation for streaming levels continuously (plus some of the Pro features to help with this are now free in 5). Unreal has level streaming. It's not that there's no support. It's that the real question is what kind of data loading does a particular game actually need.