As far as I can remember, I don't think I've run into any site or app that let's you shift UI versions. APIs tend to keep versions around. Apps keep many versions around for much longer periods of time. This could also allow for real long-term testing of UIs and features.

I get that things change, etc. But I feel the general consensus from people around me, despite their age, is frustration towards these endless changes. I'm not here thinking somehow business will start being better, but maybe this would at least be a more rational way to handle UI changes (and avoid adding more frustration into the world)?