It's not a group problem.At a certain point you have to do a secret poll of the group (no need asking the people complaining they can't break the game of course). Is everyone okay with this? If so, then you have to decide if you want to continue DMing them. If it's just one or two players you simply have to learn to say "no". Not sure what else to say.
It's a "TSR and WOTC always agree to the buffs of spellcaster fans everytime always" problem.
No matter how TSR or WOTC nerf casters at the start, they always buff them in some other way. And they continuously buff them as the edition rolls until the next edition or half edition rolls on to restart the process.
It is known in RPGs of all types, fans will always ask for buffs of their favorite class. The developer is supposed to say "no" sometimes. TSR and WOTC are/were clearly biased on their saying of "No."