Opencart 1.5.3.1

We have been told that our Joomal site using open cart version 1.5.3.1 is unsupported and we are better off going to another platform altogether? To me this is very harsh! We are being told that because of Google new rules about having a mobile friendly site that we will continue to fall in the rankings. I'm looking for some advice as the advice we are getting I believe in the best interest of the developers to re write our site.There is a lot of work that has already been done on our joomla open cart site and I don't want to re-create the wheel again. Please let me know where we should turn for level headed advice. View our site at http://www.intelcontrols.com.. Any help would be great... Thanks

If the responsiveness is the only issue you can just make your theme responsive or get a responsive theme.