I think it's a mistake for them to throw KA in the same category as traditional K-12 education in the first place. At least from my experience with it, people don't go on Kahn Academy to try to learn everything; it's more valuable when you're looking for knowledge about a specific subject, and you already have a reason for wanting to learn it.
The article's main criticism is that KA doesn't try to talk about all the possible uses of the subject matter. I'd rather they didn't, or at the very least kept it separate. Unless someone's being forced to sit down and watch educational videos, that doesn't add enough value to justify the time spent.
It may be that other competitors (including the ones you've mentioned) will try to fill the gap and take a more traditional education role. But saying something's bad just because it's not occupying the exact niche that the author wants it to? That's not a very useful criticism.
I feel like KA frees up some of the time constraints of traditional educators so that they can spend more time doing the motivation and the possible uses of a subject matter.
I'm no teacher but if I was I'd much rather spend my time getting kids excited about stuff and then point them to the resources they need to get going. I'd also have more time to answer questions so the kids wouldn't get as frustrated or stuck.