There may be a used trailer on the market in your area that is of good quality. There is also a Canadian mfg (name escapes me) that is highly regarded.
Yes current new models may contain some cost cutting materials that are less than good. The composite floor construction is something I'd avoid. My trailer has 5/8" plywood and I had to replace a small section under the water heater and a small section that was near the bathroom. The rest is original and still in good condition after 46 years.
The use of EPDM for roofing material is just economy at work. Those owners that have installed a spray-on Roof Armor coating report excellent results and since the coating is applied over vent flanges and other through holes, typical caulk maintenance isn't needed. Eternabond cures a lot of ills, too. I have an aluminum roof and everything is sealed with Eternabond tapes. I have no leaks and test with pressurized interior air every few years, now. I have my own blower so testing is easy.
The Livin lite line of trailers used to be all aluminum but have now changed their flooring. We will see. Lance makes a solid unit and Bigfoot is also highly regarded in Forum reports.
Good luck with the trailer hunt.