My thoughts on this as a newish returned angler,
First off the stats are misleading like VMP posted. That churn can be completely normal. Tons of people pick up fishing licenses, decide its not for them and then stop, sure. But a lot of that can also be attributed to cases like: I had an OR license last year, this year (so far) I don't because I don't live in OR anymore and I haven't had occasion to go fish there this year. That kind of churn is normal and unavoidable. But saying that 50% of license sales are dropped sure sounds scarier.
I will say that there does seem to be truth to the "Here's the reason why" section. Fishing is indeed hard, especially with dwindling stocks and increased threats to access. I'd also say its hard to even get into fishing and learn when, either because of reality or perception, the existing community is seen as old, gatekeeping and crotchety. I've seen countless posts on the internet (in general not saying here specifically) where someone who is clearly new asks for help only to be met with howls of "hotspotting," "go do your own research," "in the water," or even outright bad advice like pointing people to tresspass on military bases and what not. Thats of course, in between the posts about people having fights at boat ramps because someone did something that was perceived to be slightly incorrect, or screeds about having to share a stretch of river with someone. Of course there are always [fly]fishing shops, but you run into other fun walls there, like the customer who is chatting up the staff (and often the staff that is all to happy to ignore other customers so they can chat) and won't leave despite never buying anything, or the staff that decides the new person doesn't deserve their time.
One thing I've heard people mention is "Join a fly fishing club! Then you'll meet people." Well, when the clubs all have events like "Join us at 2pm on the 1st Wednesday of the month at <bar> for a fly tying get together" I'm pretty sure its obvious who the clubs are run by and what their target audience is. Of course there are groups out there who try and do things a little differently ( I can think of a shop in OR that is reaching out heavily to vets, women, and new folks) but they're also dissed on a lot for blowing spots and bringing too many people to spots.
Now this isn't a purely fishing problem. I could take my rant and replace it with shooting and its basically the exact same issue with shooting spots, gun clubs and gun people. Theres a lot of people out there who learned how to do a thing in a much different world (just as an example 35 years ago there were 100 million less people in this country and no widely available internet) and they're largely decided that things were good the way they were and anything new is unacceptable, and then gatekeep the hobby from younger people who don't/can't do things the way they were done years ago.
Just my $0.02 and observations from the past couple years.