Advertising is an issue of user autonomy and a user's security in their autonomy. Users don't want to see ads. A browser that is supposed to be "for the users" shouldn't have its main screen be something that their users specifically do not want.
For most of us, adware is a type of malware. For Mozilla, they have a tradeoff between user autonomy and cash flow. They can at least say that the bad things they do are because of the sacks of cash and not for any positive user "experience." Lying about it makes it worse, not better.
Aside from ads, there is the issue that Firefox comes with backdoors (see Mr. Robot ad) and spyware (see telemetry that can't be opted out of.)
Which bits of telemetry can't be opted out of? I've set at least a hundred things in my about:config to tamp down on it but I'm never quite sure I've got all of them.
For most of us, adware is a type of malware. For Mozilla, they have a tradeoff between user autonomy and cash flow. They can at least say that the bad things they do are because of the sacks of cash and not for any positive user "experience." Lying about it makes it worse, not better.
Aside from ads, there is the issue that Firefox comes with backdoors (see Mr. Robot ad) and spyware (see telemetry that can't be opted out of.)