I really don't see why you'd disable WebAssembly and allow JavaScript instead. Expecting developers to make a fallback for a baseline-supported feature for any reason but backwards compatibility with runtimes that do not so support WASM is extremely silly.
I also have JS disabled in Firefox on my phone. It's on by default on my laptop, as I apparently visit different sites when my butt is planted in a chair.
My wish is actually for the days of NPAPI where Webassembly would be just another plugin (like Flash) and browsers clung to mainly HTML, JS, and CSS. Then developers wouldn't be quite so keen to rely on it and the web would be much less bloated. Yes, those days are long gone... As a tradeoff, I'd settle for a simple toolbar icon that lit up when Webassembly is running, and/or a high level UI (just like Location, Camera, and Microphone) so I can enable it for just those sites that need it. I tried selling Mozilla on the idea once but they apparently weren't interested.
Baselines aren't entirely universal. I remember the days when the Mozilla (or early Firefox) browser was the only viable web client for Linux, but some sites still opted to run behind ActiveX. Today I don't think you'll find a Haiku or Amiga browser with Webassembly support, nor Firefox for Linux on IBM Power motherboards. It's easy to forget that just because most any 'nix or BSD OS has a plethora of choices, that others aren't still dealing with the "ActiveX" situation and feeling like everybody's out to get them.
