I have yet to see anyone report that using minions as-is results in an un-fun result.
I can say that minions are far easier to kill than anything near their level of XP and at higher levels can be so trivially killed as to not be worth their value in XP, giving very different levels of challenge (to un-fun result) depending on heavily minions are used.
This applies more at higher level - when you have things like large encounter area effects that hit enemies only, encounter walls, etc. Before 11th it was just an occasional 'Meh' when certain abilities were used and it made the combat feel more cheap or boring, while starting with 11th it was just like 'These are just a lie about how much XP they're worth'
As a player, I've seen minions just drop like flies to Armor of Agathys or a Reaving wand and not gotten any satisfaction at it, making the fight less fun. As a DM, I've had to treat minions differently when building encounters, making the game less fun.
I certainly appreciate minions as an option, however, so want to retain that level of ease of tracking and things dying. Tricky, eh?
At any rate, that's why I gave my suggestion - addresses both sides of the complaint. The cleric who turn undeads and goes "Okay, 18 to this guy, 9 to that guy" "He's a minion, no damage." "Wait, what?" "He's a minion, misses don't hurt him." "But, 9 damage..." and the "Okay, so you put a cage around that 5x5 section. All minions on the edges automatically die at start of their turns, roll hits for the ones in the middle... and any that don't have ranged attacks are effectively worthless now since they can't get through the wall without dying too. Ah well."