I work at a union plumbing company in a major metro area and union plumbers make very good money here (100k+).

We aren’t losing any business to YouTube. We only do service for commercial businesses, and the house engineer isn’t going out of the way to do any more work than what is absolutely necessary.

You will still need a plumber if you do a large remodel or new construction. Good on you for learning how to do more yourself, but this trend has negligible impact on the industry at large.