You don't know what to say? Well, you could start with why you think otherwise. If I had to pick just one, as a combat-focused caster? It's shield. Every time. Silvery Barbs is nice, it's versatile, you can negate a crit, make something miss a teammate. That's good. It's still one attack negated, and advantage on one swing (which is being WILDLY overstated in value in this thread). At the cost of a spell slot and your reaction, which means you can't do this and shield, absorb elements, or counterspell. Those are all things a caster is probably going to want to do, too.
Shield doesn't negate just one attack, if you have five or six things swinging at you twice each, adding +5 to your AC for a round can very well be the difference between getting spanked half a dozen times or getting spanked not at all. +5 AC can't negate crits, but it can dramatically increase your chance of avoiding attacks, and for more than just one attack. Silvery Barbs doesn't even compete if you're talking about spells for your own defense. It has a niche in that it can be used offensively, or used to help you with a saving throw or help an ally, but in its own domain shield is objectively a better spell. As it should be, since it's more limited.
People in this thread are why Wizards of the Coast should be really careful when they listen to feedback, because people genuinely do bandwagon and overreact. This spell is fine. You see people in this thread making wild, zany claims like not only is it the best first level spell (a dubious claim), but it's the best second level spell too?! That's just wrong. And the way people are arriving at this conclusion can make any spell look broken. If you come up with the case where the spell is at its very strongest and just assume it works (it doesn't automatically make something fail, mind, just raises the odds), you can make anything look super strong.
Look, I can do this for any half decent spell using the same style of argument. Example, the sleep spell: "Most fights at level one and two are against things with low hp. Sleep doesn't even allow a saving throw! If you're fighting five kobolds and cast sleep, the fight ends, no saving throw! How is that balanced?! It just ENDS the fight! This spell should just be banned."
Or, since according to some Silvery Barbs is the greatest level two spell as well, how about web? "So you're telling me you can just create difficult terrain and restrain everything in a 20 foot cube?! That's up to SIXTEEN creatures! If they fail their save, they can't move and have to use their ACTION to get out of the web! And they have disadvantage on all attack rolls, and your group has ADVANTAGE on all attacks against them? All attacks! ALL OF THEM! It's ridiculous. How did this make it through playtesting?"
I'm not trying to be an naughty word or erect strawmen, here. But would the above be convincing to you if you hate Silvery Barbs? And isn't the above obviously a dramatically better use of a spell slot? And it's not like web is even the spell everyone talks about when they talk about busted second level spells. Silvery Barbs has a function, sure. It can, for example, encourage a boss to fail a saving throw against Banishment (as an example used earlier in the thread). But in that case, it's Banishment that's doing the heavy lifting, not Silvery Barbs.
The spell just came out, guys. Calm down and actually wait to see it in play for a bit before you start talking about nerfs or bans.