I think this is true for most teams, but to me the most important thing is to be able to recognize what you have in a team every year. This is where the Cowboys fail. First, they cannot be objective about their players. Too many of them are hyped and are not as good as the front office thinks they are. They lose vision of value. Some players are good, just not worth the contracts Jerry gives them in the long wrong.
The other thing is, the owner has to be willing to go all in, and mean it. The Cowboys lost to the packers past year because they could not run the football or stop the run. They did nothing in the offseason to fix that. If anything, they made it worse. When you get to 12-5 the goal in the off-season should be to do what is necessary to get to 14-3 and to win a couple of playoff games. Upgrade the roster where needed and get better.
But it is tricky. You can do that easily if you won't sign free agents, if you overpay your own free agents, or you overvalue players on your team. The Cowboys are guilty of all these things.
The "window" is the time when a team builds a strength into the roster. It can be a QB, like Mahomes, or a dominant offensive line. Once you have something like that, you build around that. The Cowboys have failed to develop a strength and have failed to maintain the strengths they have had.