Yeah, I'll just play around it by dropping in a 0-cost spell - oh, I'm dead, because it turned into a kill own minion spell (or a bolt to my face for no benefit, but that's more common and less of an insta-lose). Or a 4 mana spell I can afford to lose? Hello Glide and game over. For me it's not a power level issue, it's a sheer variance issue and how playing around it can backfire hard - I really dislike cards that can punish you for playing right. I would honestly prefer it be a 1-mana counterspell, because that can be played around with a greater reliability.
It really feels like the bad kind of RNG - that which you can't realistically control or manipulate, and doesn't add anything other than 'whelp, guess I lose!'.