Seeing old bands/groups/musicians usually sucks. Except a few exceptions.
Eh, I'll push back a little on this. I've seen a lot of "older" bands (either in age or career or just don't tour much any more) and for the most part really enjoyed their performances. Do they sound quite as good as the tape/CD they put out 30± years ago? No, of course not. But when I was younger I didn't go to a lot of concerts and, frankly, didn't even track when a lot of bands were touring (or have the time/money to go when they were). I didn't have MTV or VH1 growing up (didn't have cable at all until I went to college, and even then was too busy to spend a lot of time watching TV).
But being able to catch live performances of some of these "older" bands has been a lot of fun for me and most have sounded pretty good (Def Leppard, Journey, Jimmy Buffet, Depeche Mode, Elton John, OMD, Berlin, Styx, REO Speedwagon, Don Felder, Mary Chapin Carpenter, Poison, Joan Jett and the Blackhearts, Belinda Carlisle, etc.) and have put forth a lot of enthusiasm for their work, and it shows. Only a few would I call disappointing (Bon Jovi and Motley Crue stand out here, not for lack of effort but the performances were just not good at all). So I'll go catch as many of these groups as I can while they are still around instead of wishing that I had when they stop touring and I missed out on the fun. I'll enjoy them for what they are and the fun they are having at this stage of their careers.