The stack is much better and I'd say more nuanced. Now you can target things on the stack specifically. There's more bluffing and playing with the fact that there is incomplete information.
However Hearthstone has no such interplay - likely because it allows an easier functioning AI and interplay in a normatively turn-based game online is difficult.
I think we agree?
If anything, it nerfed them a bit as now Instants can be cast in response to cards that would have been Interrupts.
Interrupts used to work in a fashion similar to Split Second.
How would this be possible when interrupts existed?
You have the original Wrath of God spell.
The effect or spell that allows you to sacrifice or bounce those things would be in the Instant batch.
The counterspell would be in the Interrupt batch.
The big difference is that once that counterspell is on the stack, you can't cast any more Instants.
So let's say that instead of countering the Wrath, you counter the spell that's bouncing all of the things. With the old system, that's it. If I don't have any Interrupts, we need to resolve our batches. No one can cast an Instant until we resolve both the Interrupt batch, the Instant batch, then the original spell.
Counterspells were even better before. They were effectively the last word. The stack kind of depowered them, but it gave a lot more play to the game.
I play Wrath. I can counter now, or let it resolve. You play instant effect. I can counter, but can't counter the wrath anymore. I'm pretty sure that's how it worked.
In HS it's simplified - with few exceptions, your stuff happens only on your turn, very little targeting of the player (ie, no discard). The strategies are limited. I still like it, but ... it's definitely not up to MTG richness.