For starters, Brave is still Chromium, which means when Manifest v3 drops, you can expect a lot of the adblocking extensions to stop working. Only the built-in adblockers will continue to work after Manifest v3 finishes rolling out (next month, supposedly).
You're still using a web browser that is allowing Google to dictate web standards, sadly.
I love Brave, with its built in adblockers PLUS the ability to install more on top of it, so you can turn one off and still have protection. It feels pretty streamlined.
Firefox isn't as streamlined, I agree. However, as stated above, you will likely lose access to any extension type adblockers and be left with only the built-in adblockers relatively soon. Firefox does not have this long-term problem because it has it's own rendering engine and its business model isn't based on advertising. Already adblockers on Chrome/Chromium/Brave that are extensions are able to do less to control ads than they are on Firefox, because Google's Manifest v3 is going to remove a lot of their ability to monitor the page they're on. Google claims its for "security" and it is: It's for Google's financial security.
As someone who pirates stuff pretty frequently too, all of its pop up blockers make me feel more safe.
I'm really not sure how this differs from Firefox which has had built-in pop-up blockers for a decade at least. You should be more worried about using a VPN if you're pirating, than about pop-ups. Also, it might behoove you to move towards invite-only torrent sites which you don't have to worry about pop-ups and viruses.
Should I make a switch to Firefox, and if so, why?
The main reasons why you should switch probably don't matter to you much, but here goes.
Google is dominating in the browser market, and ALL browsers except Firefox are now based on Chromium. Brave, Edge, Opera, and so on all use Google's Blink rendering engine from Chromium.
Google has a history of trying to ignore web standards and impose their own. Like trying to remove the https:// and the www to make it "cleaner" while actually obfuscating important information the end-user might want to see.
Google's main business is advertising, and anything that is going to get in their way of serving ads is going to be fought by them. Look at what is happening with YouTube, where they are going to block access to videos based on whether you're using an adblocker. If you don't think things like that are coming down the line for Chrome/Chromium, you're naive.
Google is realizing their search sucks now, that nobody trusts products they make because they kill their products so quickly and willingly, and that they're starting to hemorrhage money. They have to stave the bleeding, and that starts with fighting against adblockers, because once again their entire profitable business is ads.
If you care about open standards? Use Firefox. If you care about not seeing ads? Use Firefox.
Don't let Google dominate until they actually can start forcing the web to be how Google wants it to be: an ad infested shitfest.