I really hate whenever I try to explain how some bad rules can be abused and immediatelly get someone say shit like "If this happens in your group, change it" as if that would solve the problem. And whenever it is not soemthing you witnessed personally, then it means it never happens and could never happen.
This argument just dismisses all criticism of the rules and implies that the "game" portion of the role-playing game is irrelevant. By that logic, the design of D&D 5e (and every single rule and mechanic in it) is no better or worse than any other game, including stuff like F.A.T.A.L.
If the rules don't matter, why bother? Why buy books, learn a whole system, and go through the effort of trying to use a specific RPG instead of just doing free form role-play?
If they do matter, then they can and will impact the quality of your experience in positive and negative ways. They can be well designed, easy to understand, and effective at serving their purpose, or they can be poorly designed, incomplete, confusing or nonfunctional.
Sure, you can ignore rules when you don't want to follow them, and you can do your own thing and homebrew it if you like. You can also ignore the ending of a book and write your own headcanon, that doesn't mean that there isn't any point in criticizing bad writing.
To put this another way, why have rule books and a character sheet with all those numbers on it? Why not just flip a coin whenever you want uncertainty about an outcome? Would a game with only that mechanic be just as effective as D&D at providing the type of experience that D&D is trying to create? If not, then why not? What makes the big complicated mess of rules that is D&D better than my single rule RPG?
If you truly think that, then I contend that you didn't understand their argument.
They are dismissing one specific criticism of the rules; that they can be "abused".
Roleplaying games are a collaborative social activity. The goal should be to collectively tell an enjoyable story. Under those circumstances, no one should have any incentive to abuse the rules or their fellow players.
In other words, criticising the rules because they can be abused is like criticising the design of a hammer because it can potentially be used as a weapon. There is basically no way to design a functional, effective hammer that does not open up the possibility that a bad actor could use it as a weapon. That does not constitute a flaw in the design of the hammer, and trying to redesign the hammer to prevent such an abuse will result in a very bad hammer.
There are bad rules and good rules, but good rules are good because they facilitate enjoyable play effectively. In other words good rules should help the GM and the players do the things that are fun. The rules do not exist to create a perfectly balanced showdown between equally matched opponents, and they cannot ever exist to do that in a context where you have a GM/DM, because the overwhelming power afforded to someone with near total narrative authority makes it impossible to ever balance that dynamic. Rather, the rules exist to a) introduce an element of chaos to the narrative, and b) guide the game towards outcomes that tend to reflect the individual capabilities and circumstances of the characters involved.
And within that context there are plenty of examples of good and bad rules design. You can absolutely find, make, or customize a better hammer. But if your criticism comes down to "You could hurt someone with this if you wanted to" then you have absolutely missed the point.
There is no set of game rules that will ever prevent a toxic table from being toxic. Despite OP's objections, the only solution to shitty people in your gaming group is to either remove the shitty people, or remove yourself. I get how much that sucks, but it really is the only solution.
I just want you to know how much I appreciate your hammer comparison. That is an incredibly apt simile and I want you to get credit for it. You should feel good about your analysis and communication skills.
That's what three years of university and a lot of student debt gets me 😅 But I appreciate the compliment.