In my opinion, the question comes down to "what is a valid criticism". I think the bombing part, where a lot of people give a similar negative review at the same time is secondary.
If a game releases in a borderline unplayable state this warrants negative reviews. It shouldn't matter how many of them there are and if they are all in a similar time frame. Same with an update that harms the game a lot. If this makes the game change the rating from positive to mixed or negative, I think that's fair because if I buy the game now, I will get it in the most recent state and if this is shit I don't care if it was better at some point in the past, I'm glad if I get a warning through the reviews.
If the game gets negative reviews because a person/group related to creating the game said or did something that a large group of people disagree with it's more complicated. It boils down to if you can/want to separate the art from the artist and if you find that criticized thing bad in the first place. If you don't think this is a valid criticism you probably think this "review bombing" is a bad thing.
I think the term "review bombing" is used to imply that the criticism has nothing to do with the game itself. But like with all terms, the usage becomes broader and broader until it changes or loses meaning completely.
Since Steam reviews contain written explanations it is easy to check why the game gets the negative attention. I never came across a game that had a lot of reviews for an unrelated thing where almost all the negative reviews lied and said it was bad for gameplay reasons.
they already have a system for review bombing. i hope this is for stupid "joke" reviews that say nothing about the game but regurgitate the same fake review for the 1400th time.
I don't have a direct quote, but I remember reading a few years ago that valve was debating how to handle bombing. They said something along the lines of not wanting to silence the bombers, but to highlight it so it was clear it was a review bomb. I got the impression they were considering things like showing the unusual spike of reviews in a different color. This sounds like it might be the results of that.
They already have something for it, when I look at a review bombed game it specifically tells me that theres been unusual activity with the reviews. I believe you cna choose to hide or show the review bombs in the settings somewhere.
I've never discovered review bombing over steam. Either my peers mention it to me or I see it on social media.
Though to be fair, almost all of my decisions about buying games are made from watching videos of said game, rather than reading reviews. Steam reviews, for me, are either for very cheap games I'm buying impulsively or games where I have some insight but am still on the fence.
I used to read Rock Paper Shotgun as part of the decision making process, but I've found their input less useful the last few years.
If a game isn't overwhelmingly positive, I almost never buy it. I also find review bombs completely valid in almost every case and I'm not interested in funding games that have managed to outrage their player base. In every case I would be outraged by the same thing they are.