There was actually a number of older EA-B homebuilts at Airventure 2019. Several SX-300 and several Dyke Delta including the original. Because EAA took the effort to invite them, I think.
Arlington regional fly-in doesn't do that and was almost empty this year. I think Airventure will last somewhat longer, as the other fly-ins gradually die off.
At Air Venture 2019 Burt Rutan bemoaned the fact that nothing new has arrived in past four years. And I notice nothing new or Homebuilt related is on the cover of Sport Aviation anymore. So nothing in the magazine to grow new amateur designers to replace the old ones like Burt. And no incentive to bring new stuff like there was in the ‘70s.