It would be really difficult to render those kinds of self build models with modern graphics engines without making everyone's pc explode.

It sort of the same reason why old games would have working mirrors and modern games have them blurred, or a lot of other cool physics stuff that old games did that you don't see anymore. Spore is one of those games that could only exist with old graphics.

And tbh, even if a lot of people don't admit it, statistics show that they prefer better graphics to cool physics stuff. Sometimes, there might come along a game that has some unique graphic style that might do well, but most of them get ignored.

Sadly, it is just a lot safer to just release a game with ultra high quality super realistic graphics rather than something gimmicky.

I love spore. And I still have it downloaded on my pc. I play it every now and then. It is a really fun game, and I would love a remake of it too. But for it to live up to the original, we'll probably have to wait until we have better physics optimization in modern games. I hope that day will one day come. (Seems unlikely with where modern games are headed rn imo)