Exploitable isn't the same as unreliable- it's certainly not ideal in some circumstances as it can drain pretty heavily on momentum and be overly predictable, but it's perfectly "reliable", unlike say RestTalk which can leave you useless for several turns due to randomness, or something like Drain punch which depends on the opposing mons.
Uh yes it is.
Take this for example:
You switch into mega gallade as it sets up an SD, and you're (mega audino lets say) defensive.
So you dazzling gleam, that does jack crap, as he uses zen headbutt and puts you down to 52%~, there's a small chance for you to get 2hko'd.
So you obviously have to heal up. Now if you had softboiled, you could sit there stalling softboiled until zen headbutt misses.
However, you have wish protect.
Remember, mega audino's dazzling gleam isn't a 2hko on mega gallade, and mega gallade's +2 zen headbutt (for the most part) isn't 2hko'ing mega audino through max investment.
The thing is, when you wish, you take a hit; you don't heal immediately. Seeing as mega gallade can live one more dazzling gleam, it COULD predict your protect and get up another SD, which would seal your death.
Sure, you COULD predict him and dazzling gleam after your wish expecting him to SD again if he was in range for it, but he could also just zen headbutt again.
Your protect is exploitable and thus is unreliable; they are pretty much the same.
So basically, when you're being heavily pressured by an opponent that can set up, having wish/protect as recovery forces you into a 50/50 every turn, which is usually in your disadvantage, whereas softboiled or roost lets u stall a lot better. I understand that the scenario is a bit in mega gallade's favor here but i hope I got the general point across :S