Prebuffing is not tedious at all if you just make buffs expire quickly out of combat. "You can't just storm through anything by just expending enough spell slots", great, so instead you have a roll of the dice fight you just reload to your previous save if the saving throws don't go your way or the enemy rolls first initiative and CC's half your team and half heals the rest. ABSOLUTE GARBAGE DESIGN.
I mean, what's the alternative, you crying about prebuffing, but instead what we have is playing every single class play like a ranger or rogue and scramble for advantage before every fight so they don't miss half the attacks against a force that outnumbers you and will outlast you through sheer numbers of spells? Disregard the Githyanki patrol, just take the goblin camp or the regular Underdark encounters. Playing your way, the fights basically come down to the roll of a dice. To hell with that. To hell with being 2 shot by a minotaur. To hell with eating a 20+ damage attack from the Horrors on 30 HP pool characters with a 50% chance to retaliate if you don't abuse elevation, backstab, or light sources. To hell with a 24 damage Iron Foot.
It doesn't make you think and choose what to do at all, it's a garbage mechanic that means my druid will never use any spell but Moonbeam, or Flame Sphere/Flame Blade if they nerf moonbeam, because there's no point ever where Faerie Fire or Barkskin is ever worth the spell slot and concentration over Moonbream or Flame Sphere's reveal+damage. Actually try to think about this, don't offer some empty platitude. Explain when in hell a cleric will not use bless over Bane, when a druid will use Entangling Vines over Web (which does the same and can be set on fire) or Moonbeam.
Every time I get these same naive retorts about Concentration making for smart choices. Absolute garbage argument. Increasing spell combination permutations makes for SMART choices, not limiting your spell usage to a single spell out of 15+ 95% of the time.
Pre-buffing can always be exploited in video games when after a playthrough or load you know exactly what's on the other side of the door. It's a bad video game mechanic.
You don't need to cast only concentration spells. There are other powerful combos like Hold Person + Inflict Wounds. 8d10 with a 2nd level slot is rather nice.
Also worth noting that Larian's area and encounter design makes all crowd control spells less useful. Every fight tends to take place in a huge open area with a lot of verticality, even when you are indoors or in a dungeon. When you're being attacked by a tight horde of something spells like Entangle become very powerful, hence concentration. And also so that you can't stack multiple entangles or entangle + web on top of eachother for a super mass hold.
I do think that some spells like Barkskin could lose the concentration requirement, but the mechanic itself is cool and necessary.
