Player A casts a spell (did something), Player B counters the spell (did something)
In this case, both players did something. There was an interaction.
Player A casts a can't be countered spell (did something), Player B... (did nothing)
In this case, only one player did something. There wasn't an interaction.*
Now that doesn't mean interaction can't come later, I was just responding to your comment that counter spells are "uninteractive".
This type of play is often called "interactive", but if you are playing against a deck that does not have counterspells it feels one sided and often dumb.
@xxhazardxx Why is interaction defined as "response", you can remove things. I was one of those people that got super annoyed with someone would say mono-black control and I would say that it's not control if you cannot say no.
Is countering a spell interactive? I can assure you that the person who had their spell countered does not feel like it was an interaction especially if they have no way to counter back.
I'm not saying that I disagree you, I just want both sides of the argument here.
So I would just like to flush that out that in a deck like "Forbidian" where you literally counter every single spell (or a similar prison deck) counterspells are probably not very interactive and more like a jace fateseal.
I'd like to add that I think there are times when Abrupt Decay can be interactive. Say you are targeting a chalice and the workshop player eats it with a ravager (etc).
(I hope my analysis benefits your discussion. )