Here are my observations:
I think that millennials don't see or use the outdoors the way that those who came before them did. Hunting and fishing may be down, but at least here in California, state parks and campgrounds are full. They want to hike and bike in the outdoors, not hunt and fish. For the RV industry to pivot 180 degrees to appeal to them (and to me), the floor plan of an ideal RV needs to change from two lounge chairs facing a TV, to one centered around a comfortable bed, shower and mobile bike rack.
Millennials grew up in an era of energy efficiency, so hybrid engines, insulation and LED lights are no-brainers to them. RVs without those things seem like dinosaurs. An RV that gets only 12 mpg is completely out of the question, regardless of the current price of gasoline or diesel. They've learned that, in the long term, the price for fuel is only going to go up. They don't ever think that the price will come down to where it was "in the good old days." To them, small vehicles are much more desirable than large ones.
I'd bet that very, very few of them would ever even consider staying in an RV park. They want to boondock. Not just boondock occasionally. Whenever they go anywhere, they want to boondock. If they were to buy or rent an RV, it's got to be set up for that. They, like me, probably think that it's insane to have to level an entire vehicle so that one appliance will work. After all, the appliances in their kitchen have adjustable legs. Slide outs and things that only work with full hookups are OK in an RV park, but are serious inconveniences while boondocking. Storage designed to fit golf bags is meaningless.
Things like standard pre-wired wi-fi are assumed by millennials. They assume that there will be wi-fi in any hotel and in any restaurant. They resent having to research and find suitable wi-fi add-ons to an RV. To them, an RV with just a little solar power is a joke. They want a lot of electricity to run high-tech toys and expect it all to be powered by solar.
Also critical to those who grew up in a technological age is quality. Things that fall apart because the manufacturer is lazy or careless just won't make the grade. They grew up with 3D modeling, robot manufacturing and computer-aided design. They can't afford to waste money and they want things that last. Just adding USB ports on a dated design means very little.
Whether they buy, rent or share an RV, the RV itself has to be different. And that's the challenge for manufacturers.