The img tag isn't hugely interoperable, but it'd be a sad web without images. <audio> is a huge step up from the current madness of <object> <bgsound> <embed> or <flash>.
Are people out there really using XHTML still? It'd be interesting to do a poll to see how many are using XHTML vs HTML.
So to take your img example it would be analogous to a specification for img where Firefox was supporting PNG (but not GIF) and Safari supporting GIF (but not PNG) and IE supporting neither but Microsoft is at the same time pushing a closed source browser plugin that can show images in a Microsoft proprietary and patented format that sits outside of HTML. That would be a "sad web" too, even if it technically had images.
He's not (imho) against the video tag in any way, just pointing it out as an example of the (inherently) political squabbling and consequent craziness that surround standardization in a multi-billion pound market.