Id counter by saying

 * you trade a reaction for an action.  Thats a good trade.

* 3rd level slots are nothing expendable 7th level plus

* you can equally negate a 8th level spell from a 1st.  So imagine a lich encounter as BBEG and never getting a spell off

* Spellcaster CON saves arent great that often.

Agreed.

Thematically... it's fine. It was sort of boring when you had a Lich or something with Counterspell that just insta-counterspelled your Fireball or something, and it sometimes didn't make sense that, for instance, Vecna, could just have his spells countered.

It should be lower level, now that the aforementioned clause has been removed. HOWEVER... the " If that spell was cast with a spell slot, the slot isn’t expended." part of that clause redeems this spell somewhat, considering 99% of spells cast by monsters have the "X/day" wording and would still lose the casting of the spell.

I'm not even sure how you see a Verbal component. Mouth movement or what?

I agree, I think the only change I would want would be the saving throw to be made with the spellcaster's spell casting ability score, so it's more like, "How resilient can you cast your spell so it's not deflected/delayed?" instead of, "Can this spellcaster tough it out long enough to cast their spell?" This change would also make it more magic vs. magic than the current wording of the spell, which to me feels more like what the spell should be, as a spellcaster is trying to stop another spellcaster's spell. This would likely make Counterspell less effective, but it's still even after that a really great spell, it's just that before it was so insanely broken that you'd never see a campaign without it.

One round can be the difference between a victory and a TPK. This is especially true for larger parties, but even with smaller parties, a well-timed 2024 counterspell could mean that every single party member has a chance to stack on more damage or try to restrain the enemy. In 2014, counterspell could be thrown at any 9th level spell as a get out of jail free card if you could roll high enough. With the new rules, this 3rd level spell has to be used strategically in order to be useful, which I think is a much needed change.

In terms of grammar, an "Or" can be seen as an "and or" unlike logic gates. For example "I want a rock or a twig" does not mean I won't refuse a rock and a twig. However if I said "either a rock or a twig" then it can only be the rock or the twig, but not both.

that is correct. the logic is that to do the counterspell you need to know its being cast. V you hear it, S you see it, and M you see it. if none of them happen then you dont know its being cast to counter it/

Who wrote this change and how hard did they hit their head before thinking this was a good idea?

This is an absolute botch job of a spell. There are many reasons why this whole system update was not needed and a waste of everyone's time, but this? This right here? This is a travesty.

Oh good, so if I use counter-spell at 6th level and they fail on their 9th level roll, I lose a 6th level, but they keep their 9th. How ******* brilliant.