That may sound like valid criticism, superficially, but I think it's very fair to say that the impending death of Flash has been apparent for quite a while now and this always cast a shadow on Flex. Maybe not in the few niches that it still does survive (thrive even, in some cases), but the market that Flex aimed at was very limited early on and in the past couple of years, with Flash being predominantly a delivery mechanism for online video, still betting on Flex as "Internet Technology" seems ludicrous.
"I would have much preferred to see a transition where Flex and HTML 5 could peacefully co-exist"
If you think that, you simply don't understand the technology. In fact, many of the criticisms that are quoted seem to be this: People who are disgruntled that their bet on a proprietary piece of technology didn't pan out. Welcome to the Internet.