At least some of the Pathfinder fanbase split from Paizo the same way they split from WotC: their favorite company made a new edition, and they went elsewhere to find games compatible with their tastes/existing products.
There's definitely an issue of taste within this: I probably won't blink if presented with mindless opponents like the usual zombie/skeleton. Maybe I wouldn't think too hard about fiends. But for my tastes, sapient mortals are just uncomfortable.
I have a few elementals I'm kind of proud of:
Wood: Imagine treants who are fast, stealthy, and covered in tangling vines.
Bone: Collections of skeleton pieces with horns for claws, and that can rot wood or rust metal with a touch.
Metal: Collections of metal plates and pins, skittering around...
I have to admit: the sort of psychic powers often seen in sci-fi are often more attractive to me then pages of spells.
That could be interesting: spellcasting would be one-short (per rest) that you either save or work around.
I'm not sure I'd want to play that, though: I'm one of those people...
Which is often what I desire after reading caster vs martial threads: in my mind, the problem is that the two systems are too different to balance effectively.
A 1st level Wizard would get "Move Stuff At a Distance", which lets them move and throw objects. That's the only magical thing they...
If I were in charge of doing this, the first thing I'd do is get rid of the current spellcasting system.
I would replace it with each "magic" class having specific class or subclass features that do spell-like stuff, but only a few per class/subclass, with as little overlap as possible. There...
They should just get rid of the Wizard. Replace it with the Warlock.
Also replace the Sorcerer with Warlock.
Heck, throw out Cleric and Druid and make them Warlock subclasses: no one wants to cast healing anyway.
Bard, too. Call it "Muse Patron".
Paladin? Warlock subclass!
Ranger is...
Pathfinder 1e, unless you're counting that as part of 3.5e D&D.
My feeling is that rather than Spheres being more complex, it's different such that if you started on the D&D slots system it takes time to learn. I don't recommend Spheres if people want something that sticks closer to core 5e...
The majority of the system is based on giving the caster a few simple base effects and then further options modify those. It's kind of like how Warlocks get eldritch blast and then can take invocations that modify the blast. I find dealing with that much, much easier than having a bunch of...
How much info do you want to have to read through?
Because it'd be easy to make a psion using Spheres of Power: Incanter with the Esper subclass and focus on talents from Mind and Telekinesis.
There's also Green Ronin's Blue Rose for 5e, but that'd be buying a whole book just for the tweaks...