>What about them putting ads in the URL bar suggestions?

Not great... at least they ask you at least once to allow this, and let you disable it at any point, something that cannot be really said for some of their major competitors.

>What about them (temporarily) putting ads into the new tab page that you couldn't opt out of?

I honestly do not remember them doing that? The only thing I remember was these self-promotional things like "Try Firefox for Android" stuff, but not "real" (i.e. paid for) ads. Maybe I just forgot?

>What about them removing the ability to customize the new tab page?

Customize in what way? I can customize my new tab page just fine, edit and pin and remove things. Change the number of rows, disable "sponsored shortcuts" aka ads and Pocket (aka more ads), remove the search bar...

>What about them making it all but impossible to install your own (unsigned) browser extensions?

This indeed was not a great move. But I kinda get where this was coming from a little. There was in fact a substantial number of malware extensions out there, and somebody in my family even fell for one (IIRC it disguised itself as a video codec update).

That there is no hidden setting or "cheat code" in the release browser to override the signature requirement bugs me, tho. The rational here was that if there was an override, people would just disable checks based on recommendations on "power user" sites and/or tutorials and/or disable it because a malware author told them to, or that an external malware could override this silently to bug the browser (but that argument does not count for me; if you have some malware running on your machine already capable of flipping such a setting, you lost already, anyway). I'd say, just make it blatantly obvious that turning off signature checks is rather risky[0] and enable those users to make an informed decision (and if they do not inform themselves and just click around, that's honestly their bad).

Compared to Chrome tho, this is all still very low-level annoying. Chrome never let you permanently install unsigned extensions in the first place, and you have to use their "store" to host your extensions.

Ads... Google...

And the new tab page is also more customizable in Firefox than in Chrome.

That Firefox made and keeps making some not-so-great decisions is surely something we can and should criticize and ask them to do better. But also let's not forget here that you and me are the not the only users, and they have find a balance of features and available customization that suit most users without overburdening their own developers with the design, implementation and most importantly maintenance costs associated with such features.

Something like menu icons seems small, easy to implement and put behind a setting, but then you realize that there is a lot of maintenance cost associated with it. You have to maintain a good icon set, and do additional testing to ensure everything looks fine with the setting on and off, etc. And that's just one feature out of thousands, and each of those comes with costs, and then you need to prioritize because you don't really have the developer power to pay all of these costs. (And now we can quibble about which features to implement or to keep or to remove and so on, based on our personal preferences, but that isn't really helpful most of the time either)

At the same time, we shouldn't forget about the larger picture that Google and their Chrome browser are not "nice", but a company and their tool to enact mass surveillance for profit, which quite often behaves very unethical aside from that, maybe even with outright illegal practices, if you e.g. believe the court docs unsealed and in the news this week, or if you ever glanced at the GDPR and compared that with what Google is actually doing.

[0] I know, I know, a lot of the signature checks are just security theater, as the signing is automated after some automated checks, and therefore it is entirely possible for malware authors to get past those checks and get signed. It will stop some non-malicious extension writers from releasing their thing with known-vulnerable code patterns. On the other hand, mozilla still know what it signed, so at least they can consult their archives and rather effectively block retroactively the spread of such malware once they become aware of it. That does not undo any damage already done, but it stops further damage. If a piece of malware is targeted at single users or small groups, it may remain undiscovered and hence unstopped indefinitely. But at least this may help stop nondiscriminatory large scale malware campaigns in it's tracks.