I think other games can benefit from D&D's success, but I don't see Pathfinder being one of them. Why go to another medieval fantasy system with very similar mechanics? Especially if you already spent a lot of money on D&D. If you are going to spend money on a new system, wouldn't you want something that felt like a very different game?
When 5e got me back into TTRPGs, it has been so long since I had played any (1990 was that last year that I played any TTRPG before 2014) that I think of myself as a player brought into the hobby by 5e.
I did start to branch out after about a year of DMing 5e. Mostly one shots because of time limitations. First I started with free or inexpensive indie PDF games like InSPECTres. My first significant spending on a non-D&D TTRPG system was the new Paranoia. I've bought everything Mongoose Publishing has put out for that game. I also backed kickstarters for more high-concept games like Dialect. My most recent new TTRPG is The Expanse.
The impetus in all my branching out was wanting to play something either (1) very thematically different and (2) very mechanically different from D&D. I find the best experiences combine both. The mechanics support the theme in a well-designed game.
Pathfinder just doesn't interest me. I would play in a game if I had more time, but I'm not going to invest money in a new set of books to run a "crunchier" D&D. I like 5e and have years of material waiting to be used. I was interested in Starfinder but it seemed more like D&D in space. I wanted something more SCIENCE fiction, not Space Fantasy. That is why I'm excited by The Expanse.
Pathfinder either needs to retool and just make money by selling their excellent APs converted to 5e (Kobold Press, Goodman Games, Frog God Games all seem to be doing well with this model) or they need to come up with a compelling and innovative new game system.