True, it definitely doesn’t matter to the end user. But there’s still a tradeoff when we lose the openness of HTML & CSS. We won’t be able to choose “View Source” on a web page and get a meaningful result, for example. We won’t be able to inspect and extend other web pages in the same way with, say, browser extensions. (For example, building a functioning ad blocker would be difficult.)

Now, admittedly, we’ve already travelled a long way from the original vision of the web as a document store, and today’s modern web application are already somewhat opaque. But to some people, canvas rendering feels like a inflection point.