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.