Am I crazy thinking that we as web developers should NOT HAVE TO have to care about this? It's Google's and Bing's and Yahoo's problem to go build decent spiders that run multiple versions of the most recent web browsers inside them, and they do have the computing power that's needed.

All spiders/crawlers should see webpages just as human users see them that's the point! They should do whatever it takes to get this working, regardless the effort, because this is why they get paid (indirectly, though adds, but still...). And this is still not enough: it's any respectable search engine's duty to try and develop near-human-level AIs to be able to also extract meaningful information from visual structure, from pictures, and from hard to understand prose. And longer term, it will be their duty to develop above-human-level AIs to be even better at this than humans so they can provide even better search results.

Since when are we, web developers, expected to do the search engines' work for them?!

I expect this is just a transition phase and things will get on the right track soon.

(Note: and no, I'm not against helping search engines. Providing semantic markup, microformats and all this is great. But there is a difference between helping them and doing the work for them, on our dime!)

EDIT+: @OP: I'm not critical, what you and prerender.io are doing is awesome and immensely helpful for web developers! But you do realize that you're doing what search engines should be doing themselves, right? And when they will wake up and realize they should get into the game, they will have basically put you out of business... or buy your business, which I think is what you expect :) Anyway, good luck with it!