I think the general point stands though, that for just about every musician who was involved in DS, being in DS was the peak of their career.
Tommy Mandel would be a notable exception, having a long and successful career in Bryan Adams' band when he was one of the biggest acts in the world.
Mark also had a career after DS and a very successful one. If he won't succeed, DS would still be playing and releasing albums, no doubt about it.
Being a professional musician is a hard job to do, so I can't possibly critique anybody. It's truly hard to make a living in this profession, make a name for oneself and acquire some reputation, putting in decades and decades of work, with little to no recognition except from a very narrow circle of professionals. Or, like in Alan's case, effectively making half (or 25%) of the work, and getting no credits at all except liner notes. It hurts! I'd hate to be a professional musician.
But if you look at it from the other side, you're making history and recordings that will be heard for hundreds, if not thousands of years into the future. Certainly, Mark's music will be around as long as Earth is still around, so not bad. Eric Clapton and AC/DC are also household names, can't complain here either.
Sometimes, like Guy, or Sting's guitar player Dominic Miller, you get extremely lucky while enjoying the greatest job and no excessive fame at the same time.