I don't think sturdy juice is the prob, but sturdy smash with berry juice certainly is.SturdyJuice is good, but is by no means broken. Hazards break Sturdy, and most Sturdymons carry offensive movesets to help guarantee higher damage being done to them.
hazards break sturdy, but he can still shell smash on whoever he switched in, and most probably you'll have to sacrifice at least 1 or 2 poke and then have a strong priority to kill them off 100% or you might risk proccing their berry juice and they're back to full and you basically lose.
I don't see how this is that much different from swirlix case in which he could set up BD and unburden at first turn in many cases, and he didnt even had sturdy. The only major difference in fact is that swirlix could set up on the much common fighting types, and no one was really willing to run Poison jab or poison types specifically for that and stealth rock were much more uncommon. But now i see people running pjab and poison types alot specifically to deal with fighters or fairys -.-
It's not like smashers don't centralize the game at all, in fact, one of the biggest reasons priority and stealth rock is so common is exactly to deal with them.