I and my group gave Starfinder a shot shortly after it was published, and were about to give the Against the Aeon Throne AP a whirl. We got close to finishing the first part but gave up after the PCs' ship lost a space fight.
To me, the whole thing felt too much like D&D 3.5/Pathfinder but set in space with the thinnest of sci-fi veneers. You got classes and levels, which I can live with, but one of the things that really bugged me was the gear dependency. Even more than D&D 3.5/Pathfinder, the game revolves around acquiring loot which you convert into better weapons and armor and to some degree other gear. So a 1st level soldier will be using an Azimuth Laser Rifle dealing 1d8 points of damage, which they bought for 425 credits. Checking in on the same character at 13th level, they've spent 53,800 credits on a 5d6 perihelion laser rifle instead. That just feels... wrong. If you look at Star Wars, Leia is just as deadly with the standard-issue Stormtrooper rifle as she is with her own sporting blaster – or possibly more, given that one is basically an assault rifle and the other is a target shooting pistol.
The same went for adventure design – again, D&D with the serial numbers filed off. The adventure had at least two sections that I'd classify as straight-up dungeons.
Starship combat is also very sensitive to how many players there are. In the fight at the end of the adventure in question, the players go up against a hostile ship with a crew complement of 6: captain, engineer, pilot, two gunners, and a science officer. Each of these can do things that help with the fight. The PCs typically have a crew of 4, because that's the AP standard. So when the enemy is doing boss stuff, damage control, flying, shooting twice, and managing shields, the PCs will only be doing four of those things, which is a huge disadvantage, and one that doesn't really show if you look at the ship stats themselves.
The way you essentially rebuild the group's ship every level doesn't really sit well with me either. It is such a naked game concept that it's hard to rationalize, particularly since the ship is completely unrelated to any actual money the PCs have.
There are also way too many places where there are all too obvious "Red Queen's Races" going on, running faster and faster just to stay in the same place or even lose position. Again, starship combat is one of the more obvious places, particularly in the original printing. Your starship tier will almost always be the same as your level, and there are lots of checks in starship combat that's against something like "15 + 2 x starship tier" (I think most of these got errataed to be 1 or 1.5 x tier, but still). That kind of thing makes me feel like I'm just pushing my skill ranks down a black hole where I keep spending them but there's no notable effect. There are similar things all over the place, not just starship combat, but space combat is where it's the most noticeable.
