This year's clunker of an offense was still top-10, don't forget. The pieces are there, it just needs to pan out or be refined a bit.
I will concede that the offensive line could use an upgrade, particularly at Right Guard and Center. Upgrading the OL is a subtle way to improve the production of both the passing and running games by protecting Brady and opening holes for Ridley.
Speaking of Ridley, his fumbles lead to a down year for him, no question. But he is an explosive back who has proven that he can carry the load and be a 1,000+ yard player. If Vereen can avoid the injury bug then his production in this offense would be insane. Mix in some of Bolden, Blount (if he resigns) and maybe a draft pick or FA signing and the Running Backs look solid. In today's NFL, you don't need an elite running game to win, just good enough - and the Patriots can certainly be good enough.
At Wide Receiver, because of his contract, Amendola will return. Dobson and Boyce will return as well given their draft statuses. Thompkins will come back for camp but it wouldn't surprise me to see the team sign a player (Sanders) or draft another WR who could beat out Thompkins. Edelman also remains a candidate to return. Yes, it's a bummer how the Patriots don't have an elite #1 WR like some teams do, but the players they have, given health and development, can get the job done. Slot Receivers will ALWAYS be productive in the Patriots' system - Edelman IS NOT a 1,000 yard receiver anywhere else. To compliment the slot-heavy attack, all players like Dobson/Thompkins/Boyce need to do is draw consistent coverage outside and down the field, contribute in the red zone, make a few big grabs... really, an X receiver that can get 800 yards MINIMUM with the Patriots is good enough.
The big issue with the Patriots is how after Gronkowski was placed on IR, they had absolutely no respectable threat at Tight End. When defenses know they don't have to respect the Tight End, it makes it so much easier to defend an offense. Gronkowski is obviously a game-breaking talent, but can he be counted on is now the question? If the Pats were to acquire a player like Ebron, Amaro or Sefarian-Jenkins in the draft, it adds a whole new dimension to the offense.
In short - McDaniels will be back. He, Bill and Brady will be able to address the situation, take stock in who they have and what they project to have, make additions / subtraction however they can, and scheme an offense with the hope that one of their best players wont (allegedly) kill 3 people and be gone forever.