Intentional or not, they really contribute (in my mind at least) to the overall perception that Firefox is truly dead. Nobody even tests for it anymore, or worse, accepts that it's fine to be broken on FF.
I'm old enough to remember the days when every change I made I had to roll through multiple versions of IE all the way back to 6, and different things would be broken in different versions.
(I cringe when I look at some of the emails I had with them back when I was 11, though...)
The only apps that are noticeably worse in Firefox for me are Google Docs and Google Meet.
I honestly do not know a single site that is broken with Firefox. What breaks sites is my strict DNS filtering setup, not the browser I use.
I'm running Firefox, with containers enabled, with ublock origins (and as such "somewhat privacy conscious over and above the defaults"), and this works fine for me.
There could be any number of things that cause an individual issue, which may or may not be related to Firefox itself :-/
BTW, Resist Fingerprinting's main impact (for me) has been to increase triggering of "Click and Hold to prove you are not a bot" on sites relying on fingerprinting as an anti-bot measure (Drupal, Walmart, Kickstarter). On some of those, the developer doesn't even realise that measure can trigger, and it triggers in a background XHR (Kickstarter does this sometimes).
This is still better than some other sites like Lowes and Fedex where the entire site (Lowes) or backend API (Fedex package tracking) simply errors due to an Akamai block without any option to prove yourself. For those, you pretty much just have to use another Firefox profile with fingerprinting allowed (or another website).
https://support.mozilla.org/en-US/kb/firefox-protection-agai...
Good luck trying to figure out that is the issue if you don't keep it in mind at all times. (No matter how obvious it seems - hindsight will never not be 20/20.)
I'll note that apart from a handful of sites where it causes additional checks and occasional breakage (noted them in another comment below), I'm really happy with that setting. I leave it on by default and only have to break out a fingerprinted Firefox profile on rare occasion.
Adtech and mitigations are ruining the internet…
No it won't help. That is big problem with finger printing. It basically logs your computer hardward with the profile.
So no matter how many times you make new profiles. This can be mitigated via VM. However with bugs such as zenbleed, VM may not be enough.
Nothing is private has a good demo. https://github.com/gautamkrishnar/nothing-private That is reason why we need to not allow WEI or anything like that on massive scale.
Because the canvas is attempting to read pixels, which can be used for fingerprinting, Firefox is blocking this. But because it is being done in an iframe, there is no prompt until you open the iframe in a new tab at which point you can whitelist it, and it will work ok in the original iframe too.
In order to do that I had to inspect the page and copy the url since I can't right click on the game iframe to choose open in new tab, probably because it is capturing that.