Some of us have, and some of us still use it. The functionality and the need for an archive not subject to the same constraints as the wayback machine and other institutions outweighs the blackhat hijinks and bickering between a blogger and the archive.is person/team.
My own ethical calculus is that they shouldn't be ddos attacking, but on the other hand, it's the internet equivalent of a house egging, and not that big a deal in the grand scheme of things. It probably got gyrovague far more attention than they'd have gotten otherwise, so maybe they can cash in on that and thumb their nose at the archive.is people.
Regardless - maybe "we" shouldn't be telling people what sites to use or not use -if you want to talk morals and ethics, then you better stop using gmail, amazon, ebay, Apple, Microsoft, any frontier AI, and hell, your ISP has probably done more evil things since last tuesday than the average person gets up to in a lifetime, so no internet, either. And totally forget about cellular service. What about the state you live in, or the country? Are they appropriately pure and ethical, or are you going to start telling people they need to defect to some bastion of ethics and nobility?
Real life is messy. Purity tests are stupid. Use archive.is for what it is, and the value it provides which you can't get elsewhere, for as long as you can, because once they're unmasked, that sort of thing is gone from the internet, and that'd be a damn shame.