Most of what you mention are not really design issues - and remember, they were designed a long time ago.
They are maintenance issues:
The latches that hold the door closed should have been replaced years ago. They no longer hold because there is no spring in the metal anymore.
The temperature controls used to work. When they stopped working, they were never fixed - and never replaced with a more modern system.
The light bulbs and fixtures could have been replaced by a customized LED fixture that would provide more light using less electricity and lasting longer. They never were. I replaced all my old and fixtures both for efficiency and to modernize my home!
The heating issues and the smell issues are the result of failures to do any real maintenance. Amtrak would not spend the money because management didn't care. During COVID, they lost a good opportunity to do some real work on the idle equipment. Now, we taxpayers are asked to pay big bucks to finally repair our trains with no guarantee that Amtrak will keep them up in good condition. Reminds me of our local schools that don't get basic maintenance until the roofs leak so bad, it destroys the interior, then they ask for big money to replace the deteriorating ones. I don't know what Amtrak is thinking but I know that air conditioners, heaters, door latches, toilet seals, etc. don't last forever and I have replaced many of these on the homes I have lived in the past 50 years. The fuel and manpower they have wasted during those 50 years powering inefficient equipment and causing bad ordered cars to be replaced or emptied en route is just sinful.