It could be that most mutations do nothing bad, or that they end up being harmful in time, such as cancer. Here is one paper on the topic:

https://www.sciencedaily.com/releases/2022/06/220608112504.htm

And yes, that was my point. Evolution tends to work slowly, over millions of years, due to the low chance of a beneficial mutation occurring, and then also being selected for in a given environment. And, since environments change, what was once beneficial, may end up becoming harmful over time.