I'm not going to say that your feature request is bad (or good).
However, the feature request to create a requirement for users to comment on a post in order to downvote, would require effort from Stack Exchange's web development team. Feature requests for the web development team to get involved, usually have to first be approved by Stack Exchange's Community Management team (CMs). The CMs will often require there to be consensus on the relevant Meta page in order to even consider such a feature request. For something very specific to Chem.SE like "may we please get the mchem extension to MathJax installed?", this Chem.Meta page might be a relevant Meta page, but your feature request is asking to add code that would affect the way people can downvote, which is something for which the CMs will likely want to get consensus on the network-wide Meta page. For this I would highly recommend that you check Meta.SE to see if others have asked exactly the same question before (i.e. to see whether or not your question would be considered a "duplicate" of someone else's previous question). I think you'll see that people have tried to suggest your proposal, and failed to gain support.
Personally I'm with you, and I've even advocated that on some sites we should remove the downvote button all together. On Chem.SE I have upvoted almost 400x more often than I downvoted, and those downvotes were a long time ago (since then I have stopped downvoting all together, and on the more recently launched Matter Modeling Stack Exchange I've upvoted 4000+ times and never once downvoted! I've been critical of rampant downvoting in this Chem.SE chat room.
However, you and I and perhaps A-Chem are in the minority across the network. Your question may have been better received it was not phrased as a "feature request" but more as just a general discussion about downvoting to check the temperature of what this specific SE community wants, before considering whether or not we would have a chance at convincing the CMs to give the web development team the green lights to implement your proposed feature.
Edit: AChem's comment says "Physics, History of Science & Math, and even Mathematics do not have such persistent problems" and I wasn't 100% sure about that since in my experience I've got upvoted a lot better on Chem.SE and Math.SE compared to Physics.SE, and HSM has an Orwell-inspired user who was banned network-wide presumably for excessive downvoting, which is so high in volume that it visibly affects that small site. However I found this interesting today:
A new user asked a question on MMSE which still has 0 upvotes and 0 downvotes:
Due to the nature of that question, I looked to see their network profile and saw that they'd asked 1 question on Physics.SE, 1 question on Engineering.SE, and 1 question on Chemistry.SE before asking the above question on MMSE.
The Engineering.SE question had essentially no formatting, and no separation into paragraphs, but had a net score of 0:
The Physics.SE question was similar and also had a net score of 0:
The Chemistry.SE question was also similar, but thanks to a major edit by andselisk, and advice in the comments from Poutnik, and Nilay Ghosh, it looks significantly better than any of this user's other questions, and yet the score was -2:
Therefore, AChem may be right that the downvoting problem is unique to Chemistry (out of these science sites), and I've also observed now that Chemistry.SE users are more helpful than the Physics or Engineering users when it comes to making edits that improve the post, and giving advice about formatting in the comments.