I see a lot is being talked about React, AngularJS (even Ember): tutorials, performance benchmarks, posts, videos, libraries, etc.
But recently I found out about Mithril.js and it seems to me that is technically superior than most of it competitors (in terms of performance, ease of use and size), and yet, pratically nobody is talking about it.
Is this just a marketing issue or am I missing some crucial point here?
I think perception plays a big role. There are fairly large and high traffic apps[1] built w/ Mithril, but when someone is taking a risk to learn a new thing (and there's a lot of that in js), of course something used by google or facebook feels "safer" to learn than something used by mashape, guild wars 2 or lichess. I've seen the "might no longer be supported later" fear being mentioned more than a few times, even though the reality is that it's not really a solo project anymore - it has almost a hundred contributors - and has a fairly sizeable ecosystem[2][3]. There are even Mithril jobs[4] out there.
Another somewhat ironic issue is that Mithril's main appeal is its lack of ceremony. It doesn't ask you to drink the revolutionary koolaid of "bi-directional data binding" or "immutable unidirectional data flow" or whatever other fanciness you can explain to others to make yourself look good. It's just a tool to get stuff done. And even though that's an important metric, it's not exactly newsworthy.
re: ES6: to clarify, you can use ES6 w/ Mithril. The issue in question has to do w/ trying to shoehorn ES6 classes to be components (which are normally plain objects in Mithril). Things like arrow functions actually make things cleaner in places where you'd otherwise use a .bind for example.
[1] https://github.com/lhorie/mithril.js/wiki/Who-Uses-Mithril
[2] https://github.com/lhorie/mithril.js/wiki/Community-Projects
[3] https://github.com/lhorie/mithril.js/wiki/Components
[4] https://github.com/lhorie/mithril.js/wiki/JOBS