It's hard to take EFF seriously when they write so hyperbolically. What's clearly also the case is that Chrome extensions are one of the great modern security and privacy challenges --- to the point where multiple tech company security teams have people whose job it is just to screen them. Another detail that EFF doesn't want to share is that ad blockers are some of the worst offenders --- they demand maximal access to user data (think about how they work), and there are lots of them, not all of them, uh, implemented scrupulously.
EFF doesn't want to give you the other side of this story, because they're not an honest interlocutor.
If you had the other side of the story, you might still think Manifest v3 was a bad deal. Random ad blockers are very dangerous, but there are ad blockers that everyone trusts, and you might not want to make it harder for them to maintain their projects.
But EFF doesn't trust you to make that decision on your own.
EFF doesn't want to give you the other side of this story, because they're not an honest interlocutor.
If you had the other side of the story, you might still think Manifest v3 was a bad deal. Random ad blockers are very dangerous, but there are ad blockers that everyone trusts, and you might not want to make it harder for them to maintain their projects.
But EFF doesn't trust you to make that decision on your own.