Not to be a contrarian but I'm not seeing the issue. Those classic easy to build kits are still mostly available, there's a ton of vintage Revell, Monogram, and Airfix still stocked in my local hobby shop, available on Amazon, and on eBay. If a person wants an easy to build tank, plane, or ship those classics from the 70's-90's are still for sale. If you like tanks, I can get a shake the box and pour out a model of a Sherman, PZ.IV or Panther from Tamiya easily. Revell and Hasegawa have beautiful 1/32 ww2 fighters that are well detailed but straightforward to assemble with no PE or superdetailed aspects. The niche for easy to build reasonably detailed kits has been filled for the most popular subjects for a couple of decades. And for the P-51's, BF-109's, and Panther tanks there are still more basic kits being released. If you have little ones (my youngest daughter is 11) Meng's toon series of kits are easy to build and fun to paint catnip; she's working on a B-17 and Lancaster one literally as I type.
In the past 5 years we've got a profusion of new manufacturers for the more experienced modellers. We've got multiple tanks with interiors and the wishlists of most modellers have been shrinking rapidly as kits of more and more escoteric subjects keep coming out. Want a Mk1 Centurion? Platz just released one. Star Trek fan? Round 2 has a 1/350 Klingon K'Tinga coming out soon for less than $80. And a premade lighting kit if you'd like, no more soldering your own circuit boards and hand-wiring LEDs. New Bismarks, new Missouris, and so forth. I have a tough time lamenting the hobby when we have more manufacturers, more subjects, and more selection than we've had at any time since I started modelling 40 years ago. Never mind multiple lines of paint, airbrushes, weathering materials, and so forth. The one area that I think has taken a hard hit are the magazines. But be honest, you could pay 8-20 bucks for a magazine today or do a Google search and hit some build logs on a forum where the quality is as good, there are vastly more pictures, and you can ask the author questions. Or watch the damned build on Youtube for half an hour. For heaven's sake, Mike Rinaldi hosts a free Q&A every Friday! And th brick and mortar shops are in deep crap. But again, they basically have the niche of supplying you with stuff you can't wait three days for and you'll pay more for that. If I want to buy a kit this weekend at the shop I could order it from China today and have it delivered to me by the weekend for less money. That's not the death of a hobby, it's the death of one type of supplier. Which sucks because I like my local hobby shop but I can get a new release kit cheaper shipped to me before they get it in stock. That's just the new landscape.
I've been hearing about the death of modelling since the 90's. I would propose that we've never had it so good as we have right now.