The San Francisco 49ers have been one of the NFC's best teams for the past decade. Yet, they still don't have a Super Bowl championship during this time. There's a case to be made that San Francisco's championship window has closed. The biggest reason for this is that quarterback Brock Purdy was given a five-year, $265 million contract extension last May. Purdy was on a rookie contract before that, which meant that San Francisco could allocate all that money toward other roster pieces. San Francisco 49ers quarterback Brock Purdy | Kevin Ng-Imagn Images This gave the 49ers arguably the most talented roster in all of football. But they still couldn't convert it into a Super Bowl. But that's not to say that San Francisco isn't still talented. They boast plenty of standout players on offense and defense, several of whom should make a major impact next season. The most notable is star edge rusher Nick Bosa, who had to miss almost all of last year because he suffered a torn ACL in Week 3.…