It's not about "fault" as if it's some kind of moral argument. E.g. When the Twitter founders asked Prince Alwaleed Bin Talal to invest an additional $300 million in 2011[1], they had a set of revenue & profit projections to convince him to write that check. Obviously, their financial predictions didn't happen. Therefore, Twitter is judged harshly for not delivering.
The parent poster framed Twitter's criticism in terms of "Facebook envy". Instead, we should just look at the real underlying problem: Twitter has never made any money.
It's ok to be a much smaller company than Facebook if you're making profits and/or growing. Twitter doesn't seem to have an obvious path to profits. They also are not growing.
Linkedin is making profits. Snapchat is growing; it's reportedly losing money but at least it's still growing. Both are smaller companies than Facebook and yet they don't get the doom and gloom writings from the press.
[1]http://pitchbook.com/news/articles/twitter-goes-public-hatch...