The fundamental issue with Silvery Barbs, in my opinion, isn’t that it IS powerful, it’s the fact that it doesn’t make anyone FEEL powerful. It doesn’t do big damage like Fireball or even cripple a bunch of enemies like Hypnotic Pattern. It doesn’t have cool synergies like other broken spells such as Shield that make players feel creative. Instead, its singular function is to hinder the DM’s ability to do interesting things. Crits get negated, spells fail, attacks get dodged, and then the party gets a minor boost in their effectiveness in return for the comically low cost of a reaction and a level 1 slot. It also isn’t limited in its use the way other “No” options like Counterspell are. It works in basically every situation and can be confidently used in all of those situations because the reaction time cost isn’t anywhere near as high as similar debilitation spells like Bane that are also level 1, but consume an entire action. This slows down fights, makes tense moments fizzle out, and all but ensures that the party will come out on top of any remotely fair encounter due to the mathematical advantage they’ll accrue across multiple castings. It’s a spell that does too much for too little while still feeling “little.” As a result, I’ve never banned Silvery Barbs from the games I’ve run, but I almost always make the personal choice not to include it in spell lists of the characters I make. I firmly believe it’s not a spell that facilitates an enjoyable time at the table.