I try not to submit to conferences if I can avoid it. It's like you say, reviewers are looking for a reason to reject. I don't understand what makes the difference since it's usually the same people reviewing in both conferences and journals, but somehow journal reviewers do a much better job. Some journals have a fast turnaround even, and still the quality of reviewing is considerably better.
My second journal paper got rejected with encouragement to resubmit. Half the reason for that was because the reviewer had, I think, genuinely misunderstood the description of an experiment, so I re-wrote it in painstaking detail. I had a long section where I hammered out a proof of complexity spanning three pages, with four lemmas and a theorem, and the reviewer waded through all that like a hero, and caught errors and made recommendations for improvement. They made a new round of recommendations when I resubmitted. That paper took three rounds of revisions to publish (reject, resubmit, accept with minor revisions) but it got 80% better every time I had to revise it. I wish there was another couple of rounds! It was exhausting, and I bet much more so to the reviewer, but it was 100% worth it.
And yeah, I absolutely do my best to review like that myself. Even in conferences, which probably seems really weird to authors. But, hey, be the change you want to see.
Yeah, honestly the only reason I submit to conferences now is because my advisor asks me to. If it was up to me I would submit exclusively to journals or just to arxiv/open review directly. I think I'll do this when I graduate (soon).
As for the reason why it happens in conferences, I think it may actually be a different set of reviewers. While journal reviewers are going to be conference reviewers, I don't think the other way around is true. I think conferences tend to just have a larger number of shitty reviewers (as well as more shitty submissions). And as you note, it is quite easy to misunderstand a work, doubly so when you're reading under a time constraint. It just makes for a noisy process, especially when reviewers view their job as to reject (not improve). I just think it is a bad system with a bad premise that can't really be fixed.
For conference reviewing, I always try to write what would change my mind and if I think the authors should resubmit to another venue. But even reviewing I don't feel authors get a fair shot at responding. They can't address all my comments while addressing others in a single page.
Edit: I saw your bio. I actually have a SOTA work that is rejected (twice). Good performance jump with large parameter drop. But just couldn't tune or run enough datasets because compute limited. Conferences are fun.
My second journal paper got rejected with encouragement to resubmit. Half the reason for that was because the reviewer had, I think, genuinely misunderstood the description of an experiment, so I re-wrote it in painstaking detail. I had a long section where I hammered out a proof of complexity spanning three pages, with four lemmas and a theorem, and the reviewer waded through all that like a hero, and caught errors and made recommendations for improvement. They made a new round of recommendations when I resubmitted. That paper took three rounds of revisions to publish (reject, resubmit, accept with minor revisions) but it got 80% better every time I had to revise it. I wish there was another couple of rounds! It was exhausting, and I bet much more so to the reviewer, but it was 100% worth it.
And yeah, I absolutely do my best to review like that myself. Even in conferences, which probably seems really weird to authors. But, hey, be the change you want to see.