Sure, but I never said they said it was doomed but you can pretty much hear in their tone that they have super low expectations for universal apps (aka they don't think its going to be the cure all people want it to be). If you don't listen to Windows Weekly podcast check it out. In the last episode with Brad and Paul they are pretty tepid about universal apps because they (we) have heard the same thing since Windows Phone 7.... Just wait until 7.5, 8, 8.1, now 10. Besides their sentiment there is still no reason for someone to make a universal app. I keep hearing about this larger audience that potential developers will be able to reach but we have no idea what the adoption rate of Windows 10 will be, and also there are apps that do not need a desktop/Xbox counterpart. In the case of the latter, even if there would be a reason to make a desktop/Xbox counter part there is no reason to make the mobile version in the first place because there isn't enough users to justify it. Throw that on top of the fact that it seems a lot of young developers have some sort of animosity towards MS and it just spells an uphill battle. In that same podcast Brad brings up the point that, apparently, a lot of people in the tech industry feel we are headed towards just carrying a phone (mobile PC) that we can dock in to a larger screen to basically be our computer for everything. I'm not sure whether I agree or not but its interesting that a lot of people feel that way. More importantly Brad felt like MS basically knows they lost mobile and will just carry the mobile part of Windows along until we get to this point where we are docking our phones in to larger screens. Wow that was a lot, sorry.

TL;DR They don't think it's doomed but they don't think it's going to help much either. There are flaws in the thinking of universal apps and their applications by users in this subreddit.