The System Doesn't Matter... Except When It Does
I've played a lot of different role-playing games over my time. From red-boxed Basic D&D to the various Palladium and White Wolf franchises (a lot of Rifts and Vampire in high school, OMG), all of the various D&D editions through 3.5 and 5th, Rolemaster, 7th Sea, Shadowrun 2nd through 5th edition (and even did some writing for 4th edition! See my published works page!), and of course Pathfinder 1st Edition.
It doesn't really matter what system you are playing: if you have the right GM and group of players, you will have fun.
That said, there are varying levels of engagement with the ruleset that can provide other kinds of fun. As you might guess by the fact I've spent half of my life working on a campaign setting and associated ruleset, I like a bit of game crunchiness. A bit of rule maneuvering. Playing with systems.
Some systems are overly complex. Any time I have to use the square root of something to calculate damage for an explosive device (I'm looking at you, Shadowrun), that is a rule failure. Or sometimes a game system is so simple it never addresses anything sufficiently, requiring the GM to make up things as they go along (*cough* D&D 5e).
In both cases, you can still have tons of fun playing those games if your GM sufficiently engages you in a story, and all of the players are dialed into it. I'm in a casual 5e game right now, and I love my character, who is an archfey-type warlock. He's Cai Cadfan, a half-elf orphan, who was raised in a monastery and trained to be an illuminator, all Book of Kells-style. He doesn't understand his powers, but made a pact with the Lady with the Sun in Her Crown, a powerful Seelie Court presence. She left a mark on his arm that grows with his power: an incomplete illumination like from one of his books.
THAT IS FUN AS HELL. Even if I don't think the rules are robust enough.
Likewise, I adore Shadowrun. I liked 3rd edition best, because I think it had the most flavor, but must admit that 4th edition is a stream-lined, more rules-friendly version of the game. 5th did some interesting things, but I'm not really a fan. I still have massive fun running a Shadowrun 4th edition game though. I dropped my players (a couple of actual runners and a few wannabes) into the morning the nukes went off above San Francisco, starting Crash 2.0. It was an absolute blast (hah!), seeing them try to navigate out of a ruined building and then through a ruined city, all while evading some hyper-paranoid security forces and with a clock counting down until they succumbed to radiation sickness. They were also initially on opposing sides of the run, so it was a great session of role-playing.
So, that is a long, roundabout way of saying I've been going over the Pathfinder 2 Playtest materials. There's a few ideas I like (I already do a backgrounds-like mechanic in my home games, and I like the action economy and the idea of how spellcasting works with it). A few more that I think I could like, if they were implemented a little differently (ancestry/ancestry feats, the crafting system... which is probably the weakest part of PF1). But very little of the book engages my "rules fun" center in my brain (looking at you, Resonance Points). I'm sure it will end up being a perfectly fine game. D&D 4e, despite all its faults, was a perfectly fine game; just no one wanted to play it . And PF2 takes a lot of things from D&D 4e/5e. Lots. Polishes them up some, but the DNA is in there. Parallel evolution, maybe. Which is ironic, considering Pathfinder originally was a response to D&D 4e.
The point is, I could play PF2 in its final form and find that game perfectly fun, in the right circumstances. But I'm not going out of my way to play it. I'm not going to run it, just as I'm not going to run D&D 5e. I'm not buying those books. If others want to do those things, great. I think there is enough space for all of the systems. I personally really like Pathfinder 1st Edition, and while it has some flaws I will house rule, there is a robust, vibrant third party community behind it. I hope that community remains with the new edition releasing next year, but even if it doesn't, there will be at least one product right here carrying on that tradition.
EDIT (March 17, 2023): Well, times have certainly changed. I went from being ambivalent about 5e to absolutely loving it. Even to the point that I prefer it and I’m running four 5e games. And all of the OGL crap that somehow ended up on the right side of history in the end, with the CC license now. What a mad world.