The problem is that these players don't make any money unless they are on the national team. So none of them are going to leave willingly. Once you get the name recognition, that seems to trump performance. And like you intimated, none of the coaches have the stones to make the necessary adjustments because they don't want to get fired. Hopefully, US Soccer will see this for the debacle it was and heads roll.
During the Bronze Medal game (USA vs. Australia), there was a detailed discussion between the announcers on why the team didn't get younger after winning the 2019 World Cup. I thought it was persuasive, and a lot less conspiratorial than what you are suggesting.
They acknowledged that age was a problem for the team, particularly on the front line. But they noted several factors accounting for the decision to go with older players in this Olympics:
- The same team, with forwards who were already old by soccer standards, had won the 2019 World Cup in convincing fashion, so there was no indication then that they were over the hill.
- When the new coach took over immediately after that tournament, he and everyone expected that the Olympics would be in 2020 rather than 2021, leaving him with a very short time to prepare -- probably too little time to select and practice with a drastically overhauled roster.
- When the Olympics were postponed, it was done only a few months before the event was scheduled to take place. This again created a situation where there would be too little time to overhaul the roster for the 2021 games.
The implication is that if the coach had known in 2019 that the Olympics were two years away, he would have realized that he needed some younger forwards on his roster and would probably have selected and trained the roster differently.
Having said that, the fact that Rapinoe and Lloyd were responsible for all the scoring in the Bronze Medal game suggests that those two players in particular were far from "old timers". Both of Rapinoe's goals demonstrated a very high offensive skill level. I wonder if any younger player would have been able to score those goals.
Of greater concern is the defensive side (giving up 3 goals to both Sweden and Australia, and 2 goals to The Netherlands), where age is not a particular problem. The back end of the formation needs improvement also, though not necessarily by getting younger.