You can't "easily" manipulate it year after year. It's a myth.
It's like your domestic finances. You can borrow a bit here and save a bit there to get by. And if you stop there you can be ok. You never get even, but you can manage the debt. This is the Steve Keim way.
But when you start borrowing from one bank to pay the interest on another loan, then your into the loan sharks to pay off the banks it eventually comes crashing down. You can look flush for a while while the debt is piling up, but before long you're living in a cardboard box.
And that's where the Saints are going into next year and it's where the Rams are heading.
There's no magic trick. There is a set cap each year (consider it income) and if you're borrowing now from future income the time comes when you have to tighten your belt and live on baked beans.
Sorry, BritCard, but you are simply not basing your arguments on facts.
First, if you read the CBA you will see that the salary cap is based on revenue, and unless you believe that the revenue (especially TV deals) will suddenly start to plummet (for the first time probably ever), the salary cap will continue rising. This year the salary cap is up 25.7 million from 2021, and the amount has gone up ten years in a row.
Second, there is the history. DaHilg has already explained in this thread how you can look at the Saints and the Rams as the best examples.
As you see, your analogy about domestic finances makes sense from a theoretical standpoint, but since the salary cap goes up so much each year, it makes no sense to talk about it as a tool that restrict teams from doing business. If your salary increased 12-16% each year - and you knew with almost certainty that it would continue to happen for the next many, many years - your budget for domestic finances would be a lot easier to make.
It is a ghost to talk about the salary cap as anything else than a bad excuse.