I presume you believe gravity exists.
There are even Laws of Gravity that describe it's effects.
But we are still trying to figure out the mechanism that makes gravity work. The descriptions of how gravity works are the Theories.
So just because the mechanisms are still being investigated doesn't make evolution in and of itself a theory.
If we resume this discussion (yes, you'll find other older threads) let's not mix generic terms like evolution of the planet with biological evolution. Both meanings work in English but they are two separate discussions... that get mired together.
Theoreticallyone can believe in a 6000 year old earth AND in biological evolution. We use the mechanisms of evolution to breed our domestic animals. We see the effects of natural selection when we misuse antibiotics and create resistant bacteria.
BTW, I'm not implying I believe in a 6000 year old earth. It just looks good for its age.![]()