No, Vivaldi, Brave and Opera have builtin adblockers which don't depend on the extensions manifest. Plus, one could always rely on AdGuard, which whould block ads system wide.
Same. The adblocker in Brave is great, its been ages since I ditched uBo and I've still to see a single ad. Built-in adblockers are good, because Google has no power there. Firefox, instead, its still a thing exclusively because of uBO i.e., the work of an external, unpaid developer. The say uBO disappears, is the day FF dies. Mozilla is so busy wasting time and money on unrelated stuff and huge CEO paychechs that they have had no the time to add and inbuilt advlocker to FF, which instead has useless crap such as Pockets and an opt-out ad-measurement tool which nobody asked for.
As a Linux user myself, let me tell you that telling people what they should/must do this is how you make people plainly ignore you and think you're just an annoying person.
People will keep using what works for them, be it Windows/Linux/MacOS even if with minor inconveniences. Same goes for browsers/services/etc...
The missing 5th panel would be "I'm tired of this shit. Fuck science and research. I'm going to look for a real job". And yes, I'm in that 5th panel. Unfortunately.
Firefox doesn't have a proper adblocker. It's just a tracker blocker.