I’ve tried to make him work and you’ll notice why he isn’t OP relatively quickly:
First off, he doesn’t impact the board immediately. This becomes most apparent if you’re playing him on curve, which means he won’t be pooping out eggs immediately, either. However, even if you do ramp him out, the simple fact is that your opponent can still react to its presence and can potentially answer it. Of course, the earlier you get it out, the stronger it is.
Second, sub-par cards and plays. You normally wouldn’t run a Kujata, you normally wouldn’t hold your Flash for Jug instead of dropping a Sunsteel Defender for two, that sort of thing. It might not sound like much, but you’ll end up giving up power elsewhere - which isn’t necessary with other lategame bombs.
Third, consistency. To be really impressive, you basically need to double-flash him out at four mana. That’s not going to happen in the majority of games, plain and simple. When it does happen, once in a blue moon, it’s amazing and a surefire way to win you the match, but thus is the nature of wombo combo cards, I believe.
Fourth: Meltdown. Outside of double-flashing Jug out at four mana, I’m under the impression that playing and proccing Meltdown is a stronger option, quite often.
Due to all of those, it’s probably not nearly winning as many games as one might assume based off of just the card itself.