I don't have any advice as far as contacting CGT, but unless you have a legal reason to remove them, I would leave the old models up. I started selling here several years ago. I think my oldest model here is probably from 2013 or 2014, and I still get sales on those once in a while. As you've suggested, the quality of our work has improved greatly over the years, and our newer models will always be much better quality than the older ones. Maybe you can just lower the price of those older models to compensate for the quality? I took a quick glance at your portfolio and I honestly don't see anything there that you should be ashamed of or concerned about.
At any rate, good luck to you. Hope you hear back from support soon.