The problem is that you made a very broad and sweeping claim and then picked a very weak supporting point for it. Web Assembly may not change the game for every or even most sites but for sites which are performance sensitive it's an extremely user-visible improvement.
> Stop trying to prove me wrong and understand my point.
I think you should focus on making your point more clearly rather than defending what was clearly a. For example, you cite modules as something which is apparently a big deal for web developers but not shipped by Firefox. Sounds like Mozilla needs to get cracking … unless you know that only Safari has shipped it and the Chrome, Firefox, and Edge teams all have it available but behind a feature flag for testing:
https://www.chromestatus.com/feature/5365692190687232
That doesn't support your narrative that the Firefox team is ignoring this or that they're behind the market — and since anyone who isn't targeting only the latest version of Safari is either polyfilling or continuing to use their existing strategy, so there's an upper bound on how bad that can be, too.
Similarly, with Intersection Observer you can see that it was enabled in FF50 but had stability issues which lead to it being disabled and is likely to be re-enabled in FF54 based on testing. Unless you have some evidence that the developers who were working on that were pulled off to work on WebAssembly it doesn't seem like an especially compelling argument.
Again, I'm not saying that any of these things are useless — only that the narrative you're insisting on where Mozilla is ignoring web developers doesn't seem to be well supported by the evidence. At least for the projects I work on, I'd level that criticism at Safari or Edge first and in the much fewer cases where either Chrome or Firefox has a bug or limitation I need to work around it's about as likely to be Chrome as Firefox requiring extra work.