If you are a 12 WIS Cleric, you can cast 9th level spells.
Your DCs will just suck.
Also your spell rolls which are important for stuff like dispel magic and other counteract effects. And also for actual attack spells, of course.
You could. Do note that counteract checks are used for removing afflictions, so some important healing magic does benefit from a high casting stst.
I kind of miss this requirement. Given the nature of DCs and extra spells in first edition, it would be difficult to find a cleric player character without SOME wisdom (And other stats for other casters).
And the current system is exceptionally forgiving for MAD characters since it gives such blanket stat increases as you level. Heck, I think that you would have to actively sabotage yourself if you wanted to make a cleric at the level for 9th level spells without the wisdom stat for it (12 starting, lvl stat boosts, and then the stat boosting item at level 17).
So in practical terms (outside of a brain drain from stat damage), I mostly just viewed it as a setting thing. It is a basic requirement that helps to explain why there are not that many casters- you need people with above an above average stat, and they need to devote themselves to an appropriate kind of spell casting that would benefit from that (failure to get into wizard college might make a 8int/12cha character believe they are just not cut out for magic, and thus they don't try bard magic).
Low WIS Cleric is already a thing with Warpriests who just give up on competitive DCs since their Proficiency trails anyways.
Cleric Key Stat does force one boost into WIS, but with a WIS penalty race that could still net to 10 WIS.
For the 4x Level Boosts, a War Priest can easily be happy with 3x physical and CHA for Font.
Coming from a different system (Hârnmaster), I've always been a little bemused by the way attributes work in Pathfinder (and, I suppose, D&D). In HM, attributes are fixed at character creation. A magical artifact or spell that boosts an attribute would be very rare and/or very high level. In HM, aura is the most important attribute for a wizard, and intelligence the second most important. It would be possible to have a wizard with low aura or intelligence (for various values of "low") but unlikely - he probably wouldn't be accepted by any potential teacher, and you don't become a wizard without one.
I like the new flexibility, but it's sort of odd that the multiclass dedication has a stat requirement while the main class does not. you can be an int 8 wizard, but you can't be an int 8 fighter with wizard dedication feats. The whole thing sort of inspired me to create low ability casters in PF1 that used the spell slots of spells they can't cast for other things, i.e. arcanist exploits, and other abilities that burn slots for non-spells.
(emphasis added)
You can't, actually, with the default chargen rules. You could have an 8 Int on the ancestry step by taking a flaw, and choose not to increase it on the background step or the level 1 step, but picking Wizard as your class will bump it to at least 10 no matter what, and without a flaw from ancestry it starts at 12.
Man, I haven't heard of Harnmaster in about 2 decades. We tried it once, didn't know what we were doing, and I became a mason.
Not a bad thing to be, on Hârn. :-)
"Dwarves don't dig in rock, they just argue with it until it moves."