I agree with this. I think FORT, REFLEX and WILL are much less vague then mimicing the ability scores.
We were actually disagreeing on what goes into Will vs Fortitude. Not whether they are "better" than 6 saves. Or at least that's what I was discussing. dnd4vr put Cha into Fort and Str into Will and I had them the other way.
What makes something a CHR save? Is this illusion an INT save (hint: it's not)? Is getting pushed over a STR save or a CON save? Is fa;;ing due to tremors a STR save or a CON save? Or a DEX save?
I think making the saves the same as the ability scores was a step in streamlining, but I think it ended up removing the need for separate save (a good thing) at the cost of clarity (a bad thing).
Charisma saves could be compulsions, like intimidation, but instead charisma is used in weird places: bane and banishment. 5e is inconsistent about Cha vs Wis for saves.
Intelligence saves should be used for illusions but instead an Int (investigation) skill check is used.
Being pushed or pulled is resisted by Strength.
Maintaining one's balance is Dexterity. As is avoiding area of effect stuff.
Whole body modifications are Constitution: poison, disease, polymorph, petrification, etc.
As for Wis vs Cha, look at is as Con vs Str. Con is a bulwork, a defense. Str is power, active. So as above, Con is used to resist stuff that wants to corrupt the whole body. Str is used to resist stuff that wants to move the body.
Similarly, Wisdom would be used for anything that wants to corrupt the mind: emotion effects, Fear, confusion, charm. Where charisma would be used for stuff that wants to override the mind: compulsions
These are not hard. This is reflected (except the Cha) in my OP.
Maybe detailing what ability is used for what kinds of effects would help. Such a list does not exist in the PHB. But there is this in the DMG:
Strength - Opposing a force that would physically move or bind you
Dexterity - Dodging out of harm's way
Constitution - Enduring a disease, poison , or other hazard that saps vitality
Intelligence - Disbelieving certain illusions and resisting mental assaults that can be refuted with logic, sharp memory, or both
Wisdom - Resisting effects that charm, frighten, or otherwise assault your will power
Charisma - Withstanding effects, such as possession, that would subsume your personality or hurl you to another plane of existence
Maybe I should have led with that.