No, it's just that injuries are more damaging to the Dolphins than other teams. Take Detroit for instance. They are besieged with injuries and yet still continue to play at a high level. It's just a convenient excuse for the Dolphins.
I think that's a fair point. Our depth isn't anywhere near as good, so it's a pretty good assumption that we're a relatively fragile team.
The 49ers last weekend looked to have it a lot worse than us - and there was also a corresponding spike in penalties for them as substitute players struggled to execute Shannahan's system. Pearsall got called for multiple basic illegal formation penalties, just not being on the line of scrimmage. That stuff on top of the injuries just kills a precision heavy/finesse based system.