I want to know with the call to have spell pushback protection for all classes, why even have it as a mechanic?

Before spell pushback was limited to 3 seconds tops, when spells could be infinitely pushed back, it made sense. Putting talent points into a talent that stopped that was great. But now that all classes have built-in pushback protection, except for Mages who have to spend two talent points, why even have it in the first place?

Most pushback protection is at 70%. So you lose only 30% casting time. Make that the new baseline.

While I don't think spells should be completely uninterruptable, it makes no sense to have the mechanic, then give every class pushback protection to begin with.

It is talent creep and mechanics decay. IIRC Fire mages were the first class to get talent pushback or at least the good version of it (Frost got +hit and Arcane had 100% resistance to pushback on AM). Then in TBC they gave it to most casters but it was still fairly deep down in the talent trees and was really a reward for getting to max level (however pushback resistance is only REALLY great for levelling and PVP).

This was the reason that frost was such a great levelling spec (or you at least started your rotation with frost bolt), you didn't have to worry about six second fireballs from some mob whacking on you.

These days they should just remove it as we have come a long way from when casters were based around casting a few powerful spells* and so melee needed to delay those spells in PVP.

*In classic you were originally meant to use your wand even when raiding.

It may be baseline for casters, but that Enhancement Shaman trying to throw off desperate heals? The Feral Druid spamming Nourish? The Retadin Holy-Lighting himself in a desperate bid to stave off his inevitable demise? They're gonna feel it.

Casters took the talents anyway. Making them baseline for casters is just cutting fat, which Blizz wanted to do—yet the mechanic itself isn't a bad idea, since it still punishes those not specced for casting. However, I do agree that school-specific pushback resistances would be far more interesting.