JavaScript is a language that's easy to learn and has a gorillion features shoehorned in, to varying degrees of success. If you're relatively new to programming (just got done learning Python/Java) there's bound to be something new that you learn from JavaScript due to all its extra added features. Though these extra features are cool, over time you will slowly learn of the flaws that JavaScript has, and you will begin to associate "easy to learn with cool features" as the worst mistake that the language made. So, surely the answer must be to reduce how easy things are to learn. You will start to worship anything that excludes the less experienced and has cool features - for example Haskell or JS Frameworks - and you will denigrate solutions that seem too "simplistic and dirty". You will point to examples like C or Adobe Flash, citing that they have must have security vulnerabilities because they're accessible and so stupid people must be creating footguns with them. You will completely neglect the ways in which they're poorly designed and you will completely ignore the positives of both. Fundamentally, you will refuse to acknowledge that it's possible for software to be accessible and to be designed well at the same time.
Today, the internet is a dumpster precisely because of this false equivalency. It would be easy for Google to remove the guardrails from WebAssembly in some sort of public testing version of Chromium, allowing WASM to support fun little runtimes with 10x the safety of Flash. Artists could use software packages similar to the old Adobe Flash suite in order to make cool things again, expanding beyond the Neocities pages that are currently trendy. Over time, we could improve WASM environments to be incredibly safe, have interesting specialized runtimes and make super cool creations, a development model which basically already worked with HTML and CSS. But, because people still think accessible === vulnerable, we will never have that, and so every site will have the same hyperminimalistic slop look, and artists will be pushed onto the same shitty platforms to do nothing exciting in formats that have existed for centuries.
Programmers learned the wrong lesson in the 00s - that everything needs to be gatekept to protect people from themselves. The actual lesson was that designing things properly can let anyone make anything. Sure, the DOM doesn't satisfy people's need today, but it used to be excellently designed for its task - that's why it could let anyone build something amazing
I want to say I think they are talking about how great it would be if we could kick JavaScript to the curb and just use WASM for everything. I'm kind of in the same boat.
However, WASM currently doesn't have direct access to things like the DOM, if I recall correctly (this might be the guardrails the OP was referring to?). So, it's only really good for things that are heavy on the CPU. But, as a counterpoint, I don't think it's from a lack of effort from anyone's point. The last thing I remember reading was that there were still a lot of things being worked on to make it happen.
Quick Perplexity search: