I think there is a sunk cost fallacy going on here (or a reversed sunk cost fallacy?). Consider from the point of view of the original caster: You expend a 3rd-level slot to cast a fireball. It gets countered. Now you have a choice:
1) Do nothing. You are down one 3rd-level slot.
2) Counter the counterspell. You are down two 3rd-level spell slots, and you get a fireball.
You will be down one 3rd-level slot either way. That is a sunk cost and irrelevant. The question is, after paying that cost, do you want to expend a 3rd-level slot and get a fireball? Most of the time, the answer is yes: You already decided that was a good idea when you cast fireball in the first place.
Now, perhaps you would not have cast that first fireball if you had one less spell slot. In that case it might make sense to refrain from counter-countering. But most of the time, the same logic that led you to cast fireball originally argues for using another slot to sustain it*.
Similar logic applies from the counterspellers' point of view. They decided it was worth expending a 3rd-level slot to stop the fireball. That slot is a sunk cost. Now they're back in the same position as before: Do nothing and get blasted, or expend a 3rd-level slot and stop it.
Counterspell ping-pong looks insane when you see four 3rd-level slots burned wrestling over a single fireball, but each step is a rational choice for the person taking it.
*In fact, that logic is even stronger now. Previously, if you chose "no fireball," you could do something else with your action instead. Now you can't.
I know what you're saying, and I understand what you're getting across, I just don't agree. I don't think that counterspell is as problematic as you are implying, and a "wasted action" isn't as big of a deal for us. We have had plenty of fun with counterspell on both the giving and receiving end. (My Ebberon character is a 9th level Abjurer and Counterspell is one of his signature spells...so it comes up a lot.) I've never seen this 'ping pong' thing you describe, and it sounds pretty strange. Why would anyone sacrifice multiple spell slots and reactions just for ~28 points of fire damage? To each their own, I guess.
Now I'll admit there are times when we need NEED
NEED a spell to connect, and so we take measures to make sure it does. We will blind the enemy spellcaster, maybe blanket the area with darkness or fog, hide, move out of range, move
him out of range, trick him into spending his reaction, etc., etc. I realize that there isn't one simple solution that will work for all situations, but I think that's a
feature, not a bug. It adds an element of strategy.
My favorite trick so far was when my wizard used his of magic missiles against an enemy caster. He used his reaction to cast Shield and negated nine whole points of Magic Missile damage, but he
really should have saved it to counter the cleric's Silence spell, or the paladin's Smite.
Anyway.
I can see how some folks have a problem with it but Counterspell just isn't that big of a deal for us, and I doubt it ever will be. Sure it's handy, but it's not going to win any battles for you. An enemy that uses a 3rd level spell slot to cast Counterspell
isn't using it to throw lightning or explode a room or fly away. And he just used his reaction, too, so he isn't using it to Hellish Rebuke the paladin and the rogue can use his bonus action for something other than disengage. And et cetera. (shrug) As good as it is, it's still not something I'd use constantly.
I'm still in the "not broken, don't fix" camp.