Your complaint is about the structure of SE. It is a fundamental fact of this platform that it "encourages" rather than "discourages", via asymmetries (upvotes get more reward than downvotes). Comments can be upvoted but not downvoted. Deletion not only erases the answer or question, it erases the consequences of posting (the point loss and gain).
I disagree with the idea that leaving comments is useful, but that is because comments are severely abused (they incur no cost). There can be useful comments, but they are often buried in a barrage of, well, whatever you want to call it. Writing a competing answer is the appropriate response when you disagree with an answer.
It is a fact that there can be two competing answers, where one is more-upvoted but of lower quality. That is the nature of social media. I agree that every answer should provide supporting textual evidence, and yet very often no support is given. For example, an answer about contract law might claim that "consideration" is necessary in contract formation, but what is the proof that this is so? Proof is necessary at a certain (lower) level, and unnecessary at a higher level (at the level where the audience comprehends the fundaments of law.
A person could, imaginably, pursue a policy of always downvoting an answer that fails to give adequate legal citations for their answers (one should therefore always upvote an adequately-supported answer). You can also try to persuade others to follow such a policy. Personally, I don't get involved in the myriad GDPR questions that we get because it's just totally off my experiential radar. Should we also pursue a policy of downvoting questions that cannot be given an answer with adequate textual support? Perhaps, but that's a matter of personal choice and not something that can be "enforced". One solution is to have a panel of certified experts, analogous to SCOTUS, who decide definitively that an "answer" is correct / wrong. That just isn't what Stackexchange is.