Well, as the saying goes: How many folks (fill in your own favourite here) does it take to change a light bulb? Answer: Five, one to change the bulb and four to talk about how good the old one was.
I just changed from a 13 year old coach (upper mid-range diesel I suppose) that I bought new, to a new (sort of upper range diesel) that I bought new.
The engine is more efficient and more environmental, but much more complicated and I'm guessing much more of a PITA to keep running right over time. The tranny came with synthetic fluid as standard and that has some benefits both in the operation and life of the tranny...longer change cycles, but much more expensive when you have to do it.
New one has air disc brakes that I assume are better.
New one has air levelling instead of hydraulic. Simpler system with less additional components, less weight and complexity but much less "range of motion" for those uneven sites.
Cook top and fridge are more or less the same except the new fridge is a Norcold that I guess catch fire from time-to-time. Micro/Convection oven different brand but mostly the same as far as I can tell.
New air conditioners are "heat pumps" that do provide significant heat in moderately cool temps but with the same noise penalty that you get with normal air conditioner operation.
Full-body paint...much more common now and MUCH easier to clean and maintain. The old rig was about 2/3 paint and 1/3 gelcoat. The gelcoat part was getting harder and harder to maintain as the years piled up, despite the fact that I had kept it well cleaned and waxed.
MCD Blinds...yay..the death of the day/night shades! Functional when they worked but prone to string failure and a nightmare to keep clean over time.
Armless electric awnings...a mixed blessing. Easier to deploy and store but much less flexibility in changing the angle to provide more or less shade. Less support structure on the side of the rig...good for looks and much easier when cleaning/waxing etc. If everything is working, will put itself away if it gets windy. But, needs electricity to operate and is much more complex and potentially troublesome than the old "tried and true" A&E manual models. More or less useless if you have a curb side LR slide since they are so far above you, they provide no useful shade.
Curbside LR slides....good if you really need the room inside but makes almost all of your bay storage difficult to access and impinges on your patio space.
Side-hinged storage bay doors...good or essential if you have lots of slides, but they're in the way if you want to leave them open for some reason (like a basement TV).
The "flush-look" exterior windows....look good and much easier to clean and clean around...no ledges to collect debris and no exterior trim to maintain.
Better rear-view/side view cameras. Generally good I think but a potential distraction and no substitute for good "mirror discipline". Ya don't need colour...you just need a good picture.
Hard-surface floors in the main living area. Yes....carpet in an RV (except perhaps in the BR) was a really dumb idea.
Electronic dashboards etc.. Nice, but will be difficult to maintain/repair over time. Was difficult to find a part for my (discontinued) main display system on a 2012 rig.
My rig came with an electronic, cosmic, electric macerator toilet. Could be a good idea in theory...but needs electricity, seems to use water like a herd of thirsty camels and (I looked it up) would cost a stunning $1400 or so to replace. Sheesh...the old one performed its rather basic function just fine for 13 years without all the drama. So, on this one it's bling, not progress.
Overall quality of course depends on the builder, but I think, in keeping with the troubled times over the last few years, that some corners may have been cut. IMHO, a lot more lipstick and somewhat less pig.
My observations FWIW.