Of course there are differences In quality between models, low to high end.
I've not experienced anything I'd consider a quality issue with our 2 older campers, but I'm not well versed in differnet brands and what they offer.
But I will offer this. Campers just like homes are mostly get what you pay for. Look around your house and decide if it was "thrown together " or quality.
I call our house the "nicest looking p o s" we've ever lived in. Outward appearance is a nice looking custom home, built in 2001. Quality is HORRIBLE. ALL the window seals were blown when I looked at it the first time. All were replaced with the same cheap cr ap again before purchasing, some are fogged again.
Insulation is horrible, electrical work was done by a 7 year old, foundation sank once and was shored up long time ago, apparently they make 17 year rated shingles because they're shot too and they installed linoleum in the laundry and 1 bath! List goes on. That was just the highlight reel. Oh, pretty sure they forgot the glue gun and nail gun the day they sheeted the second floor. Squeaks more than an old barn loft.
We've had better built tract homes.
Same difference as RVs. There's good and bad.
You need to expect a few issues though. I don't think overall it's as bad as you think. Remember the Internet posts way more "issues" than praises and it's also subjective.