Can a good but unremarkable PhD student become an accomplished professor?
Yes of course.

Some PhD’s are really good at research, or they just prefer research.

Others however, like to pass on knowledge and when a student « gets » something they are pleased for them.

So being able to explain concepts to others and remembering or understanding why you found certain concepts difficult and using that experience to help other students can be very rewarding.

The downside is it comes with things like grading... But having clear marking schemes helps with that, both when you mark and when students want feedback.