Overall, it shows union rates being mostly a wash in 2023, but that's due to a large increase in total jobs that year; raw number of members went up, rate slightly declined. Black workers made up almost the entire grid increase.
The point that maybe relates most to what OP was saying:
These statistics don’t capture the number of workers who want to join unions. Evidence suggests that in 2023, more than 60 million workers wanted to join a union but couldn’t do so.