Omg just be a browser please. Desktop PWAs are still not a feature in Firefox. Search input elements still don't have a native "clear" button. Hardware acceleration on Linux is only like a year old feature. Etc.
I love you Firefox, but you're losing focus. If I wanted built-in gimmicks I'd use Edge (okay probably not but you get the idea)
I'd argue that fact checking can be more important today than anything that you've mentioned. Modern problems require modern solutions and it's natural that browsers extend their feature sets. I'd agree with you had they announced that they were planning to merge Firefox and Thunderbird.
Each step reduces the amount of users who could use the feature. If they think this feature is important, it makes sense to include it with the browser.
PWAs are great. Half the apps in app stores are just packaged browsers, we should take away the need for that bloat...using the engine of your choice would be a bonus. Plus they create the option of skipping app stores entirely, which is another step away from the Google/Apple oligopoly.
When the options are "install" as a PWA or download a bloated Electron app, I'm going with the PWA. Every time. :shrug: It would just be nice to be able to do that in FF without any kind of 3rd party helpers.
I currently install chromium on my systems additionally to Firefox, just to be able to use PWAs. PWAs are supported on Firefox Android anyway so I have no idea why they removed the little amount of support they had a year or so ago.