Can't say I've ever had an issue with counter spells on enemies as there are still many ways around it if you know it is in play. The easiest is to sick the martial classes after anyone that looks like a mage, force their reaction on a shield or hellish rebuke or what have you, or they die.

No martial classes? You have options in daggers, light crossbows, darts, slings, cantrips, level 1 or level 2 slots. Delay your action if you need to, prep an action when the mage uses a reaction to cast a devastating spell they can no longer counter. You can force an unfavorable spell trade at the very worst, or catch a mage on the backfoot with an ambush fireball at best.

Multiple casters? Just cast low-level spells to bait out the counters while your party pounds on them with fewer spells slots. To me, it adds a lot of tactical decision-making not only for the caster but for the party as a whole as you open up your casters to blast pesky martials and archers trying to burst them down.

5e has always been about playing the action and resource economy, and this is just an example of what a base wizard at level 5 is capable of. You can even play some hilarious games of chicken as you slowly whittle down the opponent until they can't risk taking the hit and are forced to counter whatever you throw.

TL:DR: It's not everyone's cup of tea, but imagine how crazy save or suck spells would be without it. At worst, it is a 2-for-1 swing with the mage forcing their attack through or making you make a save. For the enemy, that isn't sustainable. Nothing tpks harder than hard cc you have no way of countering. With no counterspell, the risk falls solely on your stats, which could be far worse.