Like I said in the Disqus comments of the article:

The author of this article seems as if he was talking about a very old version of Firefox, because saying that it has a worse memory management than Chrome… Makes no sense when all the tests show that Chromium is a disaster in this aspect…(If you don’t believe me, open 1000 tabs in both browsers and see which one is more responsive). And the bad code paradigm thing… Since they got rid of XUL and the advanced layers on DirectX11 (replaced by WebRender), that’s no longer a problem. Moreover, as Tim Richardson rightly says, since they have replaced the parts written in JavaScript and C++ with Rust, they have improved the components a lot. If you don’t believe me, you can check it with the StyleBench 2.0 test, which measures the CSS performance of each browser. Mozilla rewrote its CSS engine to Rust (Project Stylo) and now it’s better than Chromium!