If I didn’t like it, the entire rest of the game (that was presumably fine) is still there. It’s weird to me that the complaints about free options have the rhetorical slant that the entire game is now unplayable because of them. If they added a Guardian Rank that I didn’t like to the game, I’d similarly just disable it and give some constructive feedback. If the fourth DLC sucks, I’ll skip it and give some constructive feedback while playing the rest of the game. If they add a new skill tree and it’s broken/boring/whatever spooks players the most, I’ll skip it and continue to use the existing trees while giving constructive feedback.
The idea here is that if you don’t want to be a beta tester, all you have to do is skip/disable the content that you don’t like and leave the feedback to the rest of us; the rest of the game is still there, unchanged. (There’s always room on the other end of the hyperbole spectrum for, “■■■■ this game, there hasn’t been any new content for a whole two months” if they go that route).
If the design decisions are what irks the player (don’t like jumping puzzles, fights are too hard, don’t like the arena styles, combat mechanics, whatever) that’s not a beta-tester issue; the content is working as intended, and this content just isn’t for you. If some mechanic in this DLC isn’t working properly (like the drop rate apparently, though I can’t speak to that myself), that’s a legit concern.
If the design decisions aren’t to your liking, Gearbox should still hear about it, but, “I’m quitting the entire game because this one new mission is too hard” is a weird way to phrase it.
Like what do you say to someone who, for example, quit playing BL2 because they didn’t like the combat balance in the Wedding Day Massacre (ignore that it was a paid DLC, not free like this)? The rest of the game is still as fine as it was before. If you’re going to write off the entire game because a piece of free content had design decisions you didn’t like, maybe you just don’t like the game? If you like the game, give them some constructive feedback and continue to enjoy all the other game content.