Even if Fitz would have had the season that C.Johnson just had, that really wouldn't have made their team that much better. It's insanely hard to build a team around a 15+ million dollar per year wide receiver and a franchise QB. There's just too much money locked up in that duo alone. You're looking at more than 1/4 of the salary cap on one connection of 2 players. C.Johnson just set records for a WR this year...but his team as a whole only won a handful of games all season. They may be able to go to the playoffs at some point, but it's going to be very hard for them to do it on a consistent basis.
I'm not saying Fitz isn't a great WR. I think he's possibly once in a lifetime and maybe the best to currently play right now. What I'm saying is that I'm not 100% convinced that he'd even be an option if he were a FA this year, based on the fact that he's so insanely expensive. I think the only way Belichick would actually pursue Fitzgerald is if he agreed to come here for around 10 million or so, and then Belichick may not be able to pass it up. Unfortunately, that isn't going to happen.
You just can't effectively build a solid roster in the salary cap era with a WR like that due to cost. You may go far in the playoffs once out of luck (on a 9-7 record), but you won't have the room for a consistent winner like we currently do now. It's one of the reasons why the best CB in the game (arguably Revis) will be putting the same limitations on his team. It's hard to pay someone 14-15 million per year, especially if they aren't your QB who is going to cost the same if not more. I actually think that SF may be able to pull it off, but that's simply because they lucked out and developed a low cost rookie pact franchise QB via the draft. That will change when Kaepernick's deal is up.
Again, this is just my opinion and you may feel differently, but I can tell you that we've discussed this issue plenty of times in the past and the capologists on this forum agree with me entirely. I'd love to have a player like that, but he'd have to come on a reasonable deal. It's all about the value. That is Belichick's formula. Hopefully we see him stick to that while still addressing our needs this offseason.