If indeed the EU is harmed roughly the same as the UK is, then all that means is that No Deal is Mutually Assured Destruction. It's pretty clear that if Brexit means causing significant material damage to both sides, which is what all the evidence leads me to believe, then it's no option at all. That leaves either the current deal or the cancellation of the idea altogether -- after appropriate consultation, of course.
However negotiations work, I don't think it's unreasonable at all to presume that they're *supposed* to work by hunting something that works for both parties -- or, failing that, something that doesn't work for either party but that gets them at least closer to where they wanted to be. The Withdrawal Agreement is bad for Britain, but despite repeated denials, it does inevitably lead to Brexit. A drawn-out Brexit, too slow for many, but the end consequence is that we'd have left the EU, and would probably not have created self-imposed recession and severe damage to, eg, our farming industry, in the process.