The meme “Omicron is milder than Delta” was rapidly spreading to the point of being regarded as a common-knowledge fact. Countering it with “there is not evidence that Omicron is milder than Delta” was (and still is) a valid refutation.
And not just in the technical/statistical sense, but also in a principled sense, meaning “this is nothing but a wild guess and wishful thinking, and there’s simply no reason to think that”.
This will change in the next 2 weeks (or sooner). But currently, the idea that it’s milder is just a baseless hypothesis, not an educated guess.
First, the variant is still new relative to the time we’ve observed for the transition from “cases” to “hospitalizations” and “deaths”. Additionally, the data we do have seems to indicate that the prognosis could be slightly different (symptoms appear earlier, replication is slower in the lungs...). And on top of this, high proportion of cases is of vaccinated, boosted and reinfected.
The signals that point towards the “milder virulence” hypothesis are drowning in noise. It could be that it is indeed milder, and I hope as much as anyone for this outcome. Still I stand by my above statement: currently, it’s wishful thinking.