It's bullshit but not because it's overpowered. It's just so luck based that it can force people into no win situations.
For example, take a Glalie against something that can outspeed and OHKO it. The Glalie uses protect just once, and suddenly it might either be at an even bigger disadvantage, or it's now able to outspeed or evade anything the other mon was capable of doing. It's obnoxious for the same reason Evasion is, it's just infuriating to lose to something that's literally the embodiment of random luck. Imagine coming all the way to the end of a battle only for some jackass to whip out Sub/Protect/Freeze Dry/Sheer Cold Glalie and managed to kill your entire team just because he got lucky enough to get double speed on the first turn against your fastest mon. It's just infuriatingly hard to kill just because Moody is so easy to abuse to rack up boosts with that if they even set up one sub they're going to win and you can't do anything about it. It's the textbook definition of poor design.
In gen 8 it should at least be nerfed to only boost the stat by one stage so it's impossible (or at least significantly harder) to rack up insane boosts with it.
