I always find these debates weird but funny, since they are basically the same ones I saw elsewhere at the start of 5E. I remember a bunch of people saying that 5E was failing and pointing to the very slow release schedule as an example, when all that actually showed was that 5E was going to have fewer books and system bloat and focus more on adventure releases.
As it stands, from everything I can tell it looks like Pathfinder 2E is doing fine.
On the ICv2 charts it's a consistent second to 5E, going down to third back when the
Cyberpunk 2071 video game released, which almost certainly sparked some interest there. Releases are humming and honestly the output seems great. I think they may have had a bit of trouble with COVID because I think they actually get a good deal of sales from engagement and stuff like Pathfinder Society, but overall it seems like it's selling just fine. If all we're going on is anecdotes about how it's selling in someone's hobby shop and the Orr Report, I think we are scraping the bottom. The only RPG that seems to come close really isn't a singular RPG as much as a brand/franchise (
Call of Cthulhu, which has many different versions but seem to all get grouped together), otherwise it's far and away the solid #2 on the market.
I do disagree that the main base is Paizo fans, though. At this point, I think it's pretty clear that their base is 5E fans who want a bit more crunch and customizability compared to what WotC is giving them. It's how I ended up falling into it after absolutely swearing I would never play PF1 (I never jived with 3.X). Heck, I remember reading about how shields worked in the playtest and being turned off by it. Weird what happens when you get the full rules in your hands and take a look. But PF2 feels like a game that goes a bit beyond the casual, which means it might miss some of the people who aren't up for the system enabling a bunch of customization.
I'd also like to say that their switches in how they expand their line have also helped guys like me stay in it. I don't think I could have kept up with the previous way supplements were done in masses of constantly-released small splatbooks. Moving away from those and doing big theme books like
Book of the Dead, The Dark Archive, and
Guns and Gears was absolutely the way to go, in the same way 5E has benefited from not having too many mechanical expansions.