Unfortunately with all this stuff comes a cost & people don't want to pay for quality.
Compared to boats RVs are dirt cheap. Yes, there are cheap boats out there. Builders like Bayliner come to mind very quickly.
My biggest grumble with my 2007 Alpenlite is the frame. Yes, it is Lippert & it has cost me over $1500 in spring hanger area upgrades to make me feel confident with it. I am happy with weight as long as it translates into strength in the frame & quality of materials & workmanship in the house.
Over the years I have been in the process of 'marinising' my 5er. It has a battery type more commonly found on upmarket cruising boats. It also has an inverter/charger commonly found on those boats. It is wired like a boat. No more converter. As fasteners need replacing SS ones are being used. I'd like to replace the cheap RV grade hatches with marine ones but standard hole sizes are different. I'd like to replace all the cheap RV grade drawer slides with marine slides that don't run out all by themselves. Marine grade cupboard closures with double catches & hinges too. Outside needs the same attention with better hinges & closures for access doors. Too much simple cheap junk on RVs.
All this marine stuff costs $$$.
When something goes wrong, as it will with anything used, I do the vast majority of repairs myself. Repairs are usually easy. Getting access to what needs attention often is not. I'd like to have space for battery bank expansion. Space available on most RVs is enough for a couple of 6V batterys, no more. Not enough for any more than a couple of nights without a genny or solar without serious conservation of power usage.
Tankage in most units these days is a joke. What can anyone do with 60 gal or less when a water source is not readily available?