Find who is responsible for such sites and send them strongly-worded emails. If it's a commerce site, tell them they just lost a potential customer. In my experience it's usually the trendchasing web developers who have drunk the Goog-Aid and are trying to convince the others in the organisation to use "modern" (read: controlled by Google) features and waste time implementing these changes --- instead of the "deprecated" feature that's been there for decades and will work in just about any browser, and the management is usually more driven by $$$ so anything that affects the bottom line is going to get their attention. I've even offered to "fix" their site for free to make it more accessible.