Google and other search engines have brilliant people working for them who can create systems which can guess what I want to search before I have entered the entire query, and you are telling me these same people can't do something about pages using the latest technology. Sigh.
But I think, while we're making assumptions about the kind of technology good engineers should create, let's also ask Google-led Angular and Facebook-led React (and similar projects): if your library can manipulate HTML and the browser DOM, even while using async network requests to load data, why can't it take that same data and code to provide an HTML string upfront, as a "First Render"? This should be the standard way to do it. If React can re-render an input box every time I type a character, and not just generate HTML but also directly manipulate the DOM to reflect it, surely it can generate HTML for the input box upfront. (I don't know enough about the internals of these libraries, but maybe the fact that React is declarative makes this easier than it is for other libs.)
I don't think Bing and Yandex are supporting this yet though.
http://searchengineland.com/can-now-trust-google-crawl-ajax-...
I don't think anyone disagrees with this, but production sites would then have an incentive to wait until search engines have figured it out. Or otherwise suffer the traffic loss.
Google's 2014 summary of how well they do with javascript reads like "we just got this working, but there's lots left to do": https://webmasters.googleblog.com/2014/05/understanding-web-... . The fact that they went as late as 2014 before even trying doesn't inspire confidence.