I don't trust celebrities endorsing cryptocurrency, what i do is make my own findings, like what the product of the project would be used for, the activeness of their social platforms, the team backing up the project. Once i am satisfied, i can buy the coin.
That's a sensible approach.
Generally speaking, it depends on two factors I guess to determine whether celebrity's opinion is a useful proxy for determining if crypto is good
1. Whether a celebrity it well-versed and educated in crypto
2. Have they been involved in previous scams
The absence of two can be a useful proxy to further investigating the project