I dont know about that. When I was in Thailand, we only had one couple older than me (late 30s) on the entire boat of 20+ people. The next boat I was on, I was the oldest by a solid decade (My favorite on that trip were three 22 year-olds from Seattle who kept calling me ``old man'' , we still keep in touch about dive trips. My recent trip to Kona, we had a one older couple. However the rest of us were under 50, with a couple guys in their 20s. The one younger guy is back in Kona on the Aggressor as we speak (well, he is off the boat now, but he was there last week haha)
Everyone's experience is different, but if you dont think the younger generation (who are driving Tesla and BMW to their highest sales in history) doesnt have extra money for a dive vacation, I think you might be mistaken.