I agree the floor gets cold, but some rubber workout mats help a lot. The exposed water lines make winter and cold camping a bit of a pain. I am very strong minded when it comes to the new "improvements" in the line. I had a jayco prior to my camplite. The 5 year old roof had a leak which resulted in replacing the entire roof as well as the sheeting and some structural wood. I also had to replace part go the floor where the water rotted out. The quality of that trailer was pitiful at best and they really made no provisions for repair. Once I found camplite I immediately discovered that most if not all of the flaws in the Jayco were addressed and eliminated in the superior design. The aluminum roof is loud in the rain, but is awesome for durability and longevity. The aluminum floor is bulletproof. Access to wiring and plumbing is excellent. The welded structure is amazing. The lack of wood was a great asset. Ironically one of the only common problems was from a door that they purchased from challenger that has a habit of corroding and blistering. Overall with the materials and design, and proper maintenance, an older camplite can be preserved and used for decades. As an engineer I can almost see where they identified weakness in the other's design and corrected it. As for the new trailers? there are still some great features carried over from the original design, but the mission is getting lost to the profit margin. Just my thoughts and observations...
Don't disagree with a thing you say.

My 2013 21BHS has had its issues, especially leaks, plus a failed air conditioner. However, the knowledge of no wood is a HUGE comfort and plus for these trailers. However, to me the biggest positives are many of the issues you note; welded frame (both chassis and trailer structure), aluminum roof, etc. I too am an engineer (mechanical) and really appreciate the design of this camper. I do have the issue with the entry door, and wish they were more careful with their product selection. I also much prefer the aluminum roof. One issue they mentioned regarding the aluminum roof is the difficulty bending the material in the front of the camper. That is an ugly area on my camper when looking at it on a ladder. In fact, it is the area where the leaks in my roof formed due to the nature of the bending of the aluminum. So that would be a benefit of the rubber roof; but that is not enough to sway me to think the rubber roof is better.
I too really like the aluminum floor; especially since it is NOT wood and won't rot. The new floor, IF designed properly, may function just as well and deserves a chance. Also, for me, the cold issue with the aluminum floor is mitigated by the fact I live in Florida. My trailer has the bare aluminum flooring, which can be a bit of a pain in terms of marking and difficulty cleaning. However, if I was offered a new 21BHS in an even trade with my 2013 21BHS, I would not take them up on it. One of those new CL23 models may tempt me though if they had the aluminum door package (with those great door latches which I will never trade away).
Ultimately, the big plus is durability. My Camplite remains as solid today as when I picked it up over 4 years ago. As it currently stands, for the most part, the new Camplites retain enough of the design to still be a really durable camper. Hopefully that won't change.