Here are the problems I have with this type of reasoning:
1. It's incredibly hard to win multiple SBs, particularly in this era. None of the other 32 teams have one more than one in the last 10 years.
2. Even if Brady is a once in a life time player and BB the same for coach. In the 40+ year history of the SB only Montana and Bradshaw have more SB wins to their name - both pre Cap. Knoll is the only coach with 4 SB. Etc. etc.
3. In other words, the Pats are currently somewhere in the top five "dynasties" of all teams to have EVER played the game in the SB era, yet you chastise Pats fans for having standards that are too low? Who is being unreasonable here with expectations? The best coaches and players that ever were get 3 or so SB titles. Maybe a team that is great gets 5.
4. You seem to be asserting that BB/Pioli can do better, but just lack the proper motivation or sense of urgency. I'd suggest points 1 to 3 just suggest that NO coach, player, or team is THAT good. Ever. Under any circumstances.
You sound like that parent of a 8 year old kid who's already taking grades two levels above everyone else in her generation, comes home with a 97 on a test and you gripe about the 3 problems she got wrong - "We studied those dear, how are you going to get into Harvard with grades like that?!"
High expectations are one thing, expectations to do what no other team has ever done is just ridiculous.