We can all agree that after 10th level, game breaks down in some places, and main reason is specific spells from 6th to 9th level.
Ah boy, here we go. Any time a thread starts with "We all agree that --", I can almost guarantee that what comes next is going to be a niche case that few people actually agree upon.
I don't think that
everyone will agree. Even among those who might agree with the part about the game "breaking down" (whatever that means) after 10th level, not all of them will agree that the main reason is certain spells. There are plenty of threads here that blame any breakdown on the Fighter, or the Challenge Rating system, or the prevalence (or absence) of multiclassing, or the golden oldie of "bounded accuracy," or whatever else the hot topic of the week happens to be.
Anyway. Sorry about the tangent; people assuming I'm automatically going to agree with their opinions by default is a pet peeve of mine. Back to the topic at hand...
Low-effort solution:
If high-level spells are causing problems in your game, there is an easy way to remove them. Just inform your players at Session Zero that there are no spells available of Xth Level or higher, where X is defined as the "sweet spot" of spellcasting According To You
TM. Casters still gain spell
slots for Level X and above; these higher-level slots are used for upcasting other lower-level spells. Like casting Magic Missile using an 8th level spell slot.
A friend of mine is running a D&D campaign where there are no spells of 2nd level or higher....all magic is either a cantrip or a 1st-level spell, or a ritual. Everything else comes from a scroll or other magic item. I don't have all the details (I'm not sure what she does about high-level warlocks, for example) but her group seems to like it.
Labor-intensive solution:
Rework all spellcasting classes to spread out spell slots more evenly according to your preference and the needs of your campaign, then revise or surgically remove all of the spells that you believe are problematic. Print out these changes, and present them to your players at Session Zero. Let everyone know that these changes are still "open," and that you might need to revise and adjust them as the campaign progresses. Be especially diligent about synergies and loopholes that might develop from certain feats, or from multiclassing...some issues might be hard to spot on paper but become problematic later on in play.