Comment by ferbivore

Browsers have decent backwards compatibility for regular webpages, but there’s a steady stream of breakage when it comes to more complex content, like games. The autoplay policy changes from 2017-2018, the SharedArrayBuffer trainwreck, gating more and more stuff behind secure contexts, COOP/COEP or other arbitrary nonsense... all this stuff broke actual games out in the wild. If you made one with tools from 10 years ago you would run into at least a couple of these.