Ross is responsible for this fiasco.
I'm still waiting for Ross to hire a "real" Head Coach and GM after firing Sparano and Ireland. Actually, IMO the main reason why this team sucks is Ross; he's the one who hired Philbin, Tannenbaum, and Gase. I'll explain my reasoning:
When Ross took over the team, and before he decided to fire Sparano, this is what he had: a decent defense (with a Top 5 Rushing Defense), and a vanilla offense that settled for FGs rather than scoring TDs because they lacked above-average talent at the offensive skill positions (QB, WR, RB, and TE). Their defense kept them in games, going toe-to-toe with "elite" teams, but the offense just couldn't score enough points to get the wins. They could have been transformed into a playoff caliber team just by getting a better OC and replacing Ireland with a GM who wouldn't refuse to select players at those skill positions early in the draft. But no, Ross decided to hire Philbin, a Coach who wanted to completely change everything about the team. Coyle's change of the defensive scheme neutered that Top 5 Rushing Defense, and Philbin's personnel decisions resulted in talented players being replaced with inferior players. Blame Philbin, Gase, and Tannenbaum for the current o-line troubles; Philbin preferred players like Jonathan Martin and Dallas Thomas over someone like Incognito (recent Pro Bowler), and Gase and Tannenbaum went with the status quo instead of building a new o-line. The hiring of a new regime was the perfect time to start rebuilding a roster full of inferior players. Far too many of Miami's starters would be lucky to be a back-up on a quality team. Unfortunately, Gase and Tannenbaum decided to apply band-aids to fix gaping holes and a severe lack of talent.
Sparano's defense was one of the few in the league that gave Brady fits; it was his offense that couldn't score enough points to wrest the Division Crown away from the Pats. One or two decent drafts with a real GM and a better OC calling plays could have turned this franchise around quickly, but Ross set this team back years by hiring Philbin. Ross may really be trying to build a winner, but he keeps making poor decisions.