What he calls out as stupid was the mistake of using those technologies for the UI.

Although I defended Vivaldi as the Opera Successor since its Beta, I stopped to support and suggest it because it failed to fix the js/css/HTML sluggishness with Version 1, and even more sadly with Version 1.2. I started using unofficial stable Chromium Builds with Codecs and Sync disabled via ChrLauncher and couldn't be happier.

What do you expect from a non native UI which is rendered by the Chromium extensions system? It only can be as fast as the used System is.

So, Vivaldi is nothing at all for people who value speed more than functions. But for people who value functions over speed, i can see that these could be drawn to it.

Try Otter too, it's promising as an Opera successor, although it's still lacking some stuff like password manager.

Like Atom? So it is not unique. We can say this statement for a lot of software products being Chromium more special and from a third party.

Also like Firefox, XUL is XML + CSS + JS. And that's what, close to 20 years old now?

Is Atom a web browser? :)

I'm pretty sure that they mean Vivaldi is unique as a browser built entirely using modern web technologies.

PS: I'm not saying they're right, I haven't researched to find out if there are other HTML/JS based browsers (aka with browser chrome built in HTML/JS).

Unique?

What a joke.

It just loads other websites inside an iframe. That's how all similar web-based apps and web-OSs work. Eg there is also servo with its HTML based UI; there is WebOS with its browser, ChromeOS with its browser; FirefoxOS; etc - totally non unique beside it has a nice UI inspired by the old Opera 6-12 UI.