I know it's not particularly uncommon for web sites these days to drastically change things and in fact most people consider this a feature. The fail fast mentality is great and all except that it means you are often failing more than not and the general consensus seems to be that it's perfectly acceptable to do it in public to the detriment of your users.
There are a few patterns that I really wish would die. One of the worst offenders are single page "apps" that hijack the history navigation controls of your browser to keep you from having to download the 20MB of JavaScript on every page load making it next to impossible to refresh the page after the inevitable crash of the script somewhere in the dark mess of the minified JavaScript source. The other is the continued fad of styling the native browser video controls and overriding the functionality that is built in to provide "a consistent look and feel across platforms." This wouldn't be quite so annoying if it didn't almost always break in some unique and fun ways and omit features that the developer didn't have on their personal laptop. I don't think I've seen a single video site that skinned the HTML video element that provided a native full screen view or picture in picture on macOS. I find those features really useful and Apple worked very hard to optimize them for performance and battery life so it would be great if people would just leave them alone.
To move from a general rant to something slightly more specific here are a few examples from the latest YouTube redesign that really drives home the level of amateur hour that keeps infesting the web.
This video was not vertically letter boxed
I know CSS is hard, but come on Google...
Yes, I always wanted to scroll left and right to see my whole video
Insert sad trombone here.