I really appreciate the focus about downvotes. And I somehow disagree with the other answer that stating that asking the curators for their reasons to downvote is a bad thing.
Of course, that survey itself should be fully optional. The system should NOT force you to answer the questions in order to get your downvote out. Meaning: after one votes, then there is a "your vote has been registered, are you willing to answer a few short questions about it now" moment.
Nonetheless, that other answer has a good point: the amount of information that you can gather that way is very limited. Making a bold statement, I would claim that 90+% of all votes on stackoverflow are just legitimate curation. People notice low quality content, and they want to tell other users about that, and give an incentive to the author of that content to do better.
Thus: as long as A) users come in and are able to drop low quality content and B) that downvote system is in place, there will be that conflict. Coming from there, the only true value I see in this survey: it could help you to better understand to categorize downvotes, which could help you to implement a system that can better categorize itself. In an ideal world, the "new question" wizard has a final mandatory step were some AI tells you for real "your question doesn't meet our quality standards" ... and where you have to click like 5 times to still post it as is. (and if you do that, and then the post gets downvoted, closevoted, ... that means you get question banned the 2nd time you do it or so). Of course, getting such a system right is still hard, but probably more "doable" than 10 years ago, given the progress that AI brings to the field.
Coming back to the other answer: I started to do more curation on stackoverflow on the java tag for the last weeks, and seriously: downvotes aren't the problem there. The biggest problem: tons of low quality questions, and maybe: not enough upvotes on the few good questions. So, yes: it is great that you look into downvoting, but the downvotes aren't the problem. I very much prefer to click on a question, find it "valid", and "worth answering", and putting down an answer. Compared to downvoting, close voting, delete voting it. And commenting it, to almost never hear back anything from the OP dropping their (home)work onto other people.
The other part here: I am quite grateful that you will continue to improve the "review" queues. Where: UI changes are the smaller thing for me, it would be much more important to revisit the definition of these queues, and understand if there is actually any sense in doing things that way (please remember that many many people have complained about the utter failure that triage+help and improve have lead to). But of course, that would be a real piece of work to tackle.