I believe there’s some thinking now that dinosaurs weren’t doing all that well, stagnating, so without a meteor and volcanic activity they still would have changed in some manner eventually. But perhaps not enough to let the mammals fill any niches.
What gets me is how long life was on Earth just as single cell forms, and then suddenly, recently, it took off to bigger things.
The good news is that it will never get to that point. Venus is a different planet with a different makeup and history.
The bad news, it doesn’t have to get nearly that bad to be bad for us and the rest of existing life. Not even close. Just a few degrees more, and we’re doing really well in getting there.