That's what happens when you handwave arguments you don't like away.
That 55+ is increasing in workforce participation blows your argument out of the water. The long-term formerly unemployed, out of the workforce population (around 5 percent or so), aren't likely to ever get back in.
I'm sure 5 percent doesn't sound like much to you - but it's huge. Getting that 5 percent working was a major part as to why the boom of the 80s and 90s happened. We're back to the 70s and only about 2 or 3 percent over 1950. If we go back another 5 or so, we'll be back to where things were after the second world war.
It's possible, and if you see it happen, we could even see less than half of the population engaged in productive work. Which is going to fuel the oncoming deflationary depression that's just started.