In Tasha’s Cauldron of Everything p.134, there is a magic item: Rhythm Maker’s Drum. It gives bonus to spell attack rolls and spell saving throw DCs of the user depending on rarity: uncommon +1, rare +2, very rare +3.
Even though the same +X for a magic weapon is normal, and some weapons have specfic extra effects, it seems a dodgy for spells, because that is +X for every spell attack roll, with all their different extra effects covered. But then +3 save DC for "save or suck" spell effects, like 1st level Ray of Sickness or 4th level Polymorph, just seems way out there at any character level.
Question: Am I overreacting, is there something I am not seeing? Or is this drum, and any similar item, just something which a balance-concerned DM should not allow anywhere near their table, or maybe limit it to +1 version and making that very rare or something?
Reminder: I’m not asking for opinions. An answer like "it’s fine" or "it’s broken" must be backed up by facts (other items, rules quotes, sage advice…).