The Chargers were so far out of cap space they had to redo Bosa and Mack's contracts, didn't bring Ekeler back, and asked Allen to take a pay cut. If they made noise about the cap being a big deal, it's because for them it was.
The Saints are constantly in some level of cap pain or hell going back to Brees. The Micheal Thomas contract. Their defense. Their OL. It's big contracts and they keep kicking them forward. They will continue to with Derek Carr's contract. That's just how Benson goes - he'd rather be in cap hell at 9-8 then have one or two years of purging to get everything clear.

The Dolphins gave Tyreek a yacht full of money, now they have players up for contracts and can't keep them. They weren't going to be able to keep Wilkins, not if they are keeping Tua.

List goes on. Almost every team has cap decisions to make except a few that have a lot of expiring contracts or just have many players they don't want to keep. The Bears have been an example of this in recent years. The teams that have a lot of cap space to spend and aren't in some form of cap pain are often the exception. And yes, they often suck because they don't have big money allocated to good players or an at least average-level starting QB.

When you don't have talent, you don't pay it.