For #1, if the enemy spellcaster always nerfs counterspell, why even have counterspell? It's also annoying, it feels like the DM is not playing "fair".
Don't always do it. Read what my question was and recognize there was a condition there. D&D is an RPG. You're telling a story. It is great to have the NPCs act intelligently.
For #2, it's just boring and swingy. If it works, you just shut down what should have been a boss. If it doesn't and you've compensated thinking the caster would be shut down, what should have been a medium (or even easy) fight becomes a TPK.
If those are the only options in your mind, you're ignoring ample evidence that other possibilities are not only possible, but more common.
For #3, I'm a player as well. In addition, in the game I played where it was a major tactic, yes it was boring. I have no issue with the players stomping on my encounters now and then. But when it's the same tactic? Every time? No clever tactics, no stress just "nah, don't bother"? It's boring for me.
Try using some non spellcasters if they always use it - because that means that almost all combats have a spellcaster. Counterspell only comes up as a possibility in about 10% of my encounters (of the appropriate levels) because only about 1 in 10 features spellcasting (if that.... probably less).
However, I will note that when you have a class like sorcerer in play, which knows very few spells, you have to realize that repetition of spells is expected in 5E.
For #4, well I wasn't the DM for the campaign where this was a major issue but then it still goes back to difficulty of planning. Do I assume my biggest spells will be countered or not? How do I balance it? I have no clue how many slots they will have for a particular fight.
How do you plan for the breath weapon of a dragon? Will they use it once? Every round? How many PCs will be in it each time? Will the PCs save?
And what about those battles where the PCs roll nothing but ones and the DM rolls high all the time?
PCs can handle a range of difficulty. Not a single point. In that video I reference above there are
three meteor swarms cast - and none of them were countered. If I told you that the bad guys were going to unleash three meteor swarms on a group of 5E PCs, most people would assume that was an immediate death sentence.
I get high praise for running fun games. I simply don't have a good way of handling counterspell other than to never use casters or have them use tactics that nerf the spell after a certain level. Since I always have a goal of running a game to 20th level (and having more than a session or two at 20th), it is an issue for a significant portion of the campaign.
Then - seriously - it would be well worth your time to watch the videos I have posted above to see how it can be a very exciting and engaging addition to the combat at 20th level. There is a video of just the uses of Counterspell throughout Critical Role as well (I posted that as well).
In the end: Many DMs run the game in a way that Counterspell is an exciting and engaging addition to the game. If you struggle with it, there are resources to help you make it a better experience. You don't need to use them, but so far it seems like the 'boring factor' is a self fulfilling prophecy - it is boring because you treat it as boring.
I have run a few campaigns to 20th level in 5E. I have played in a few as well. There were a lot more higher level games that did not go to 20. I've played one bard, as well as sorcerers, warlocks (who very rarely used it - but they were clutch uses) and wizards that have it. I've seen frustrated DMs who didn't like that we used it, but I've seen more DMs who use it as a moment for scene chewing frustration that makes the PCs feel
bad %$# - and a lot of situations where the PCs hearts break when they realize they're 65 feet away when the key spell is cast.
You're free to banish it from your games - but I think that cuts off some very fun opportunities.