In addition to what
@TomRicardo said - unless you are independently wealthy, have a plan to get there fairly quickly or stand to inherit a great deal of money so you can buy a sports team and employ players, I don't see why you are against athletes getting the absolute maximum - the contract length is an accounting trick to get to the right AAV. Those last few years that look really risky when the player is 30 or 40-something are likely considered to be nothing but upside to the teams who pass them out. In many other industries companies continue making payments to former employees long after they have moved on so while it looks odd to have a former player still collecting checks, its a common occurrence in business. Why should this be viewed any differently?
What is remarkable is that sports fans, and Red Sox fans in particular, are really worried that the team stick to a sensible budget. Ownership has managed to convince folks that the players, whose MLB career expectancy is somewhere around five years total, are asking too much or that the teams that choose to play in the high end market are going to come around to the FSG way of thinking eventually. Its hard to argue with ownership's approach when the brand loyalty is this strong.
At some point, maybe people should consider that the parameters introduced by Sox management aren't a function of being clever and disciplined about team building or that these crazy contracts being handed out by the big spending clubs aren't maybe so crazy, especially if we were able to get a good picture on revenues (though the stuff you can find online, to the extent that its accurate, suggests that revenue growth is still outpacing salary inflation). On the other hand, maybe this is the right way to run this team, with this ballpark and fanbase. We just don't have enough information to get an accurate read imo.