That's right, the music itself is great and performances from when they were in their prime are fantastic. But middle aged people playing this sort of music just isn't right... 
Shouldn't you have added 'in my opinion' after that remark?
You see its just not fair to say that.
Given that millions of people still wish to pay to see the supergroups, then they will (and should) continue to perform.
I will be off to see Motorhead in Manchester again soon, they are downright ancient, but seeing as they aren't likely to get any younger and I love the music, what am I supposed to do?
It's a supply and demand thing when all is said and done.