It's a good description of the biology, but I don't think you've quite made the case you need to. There are two other important factors that mitigate the danger of widespread Omicron.

The first factor is that we already were failing to contain Delta in any meaningful way. Yes, quite a few vaccinated people were not catching Delta, but in the U.S. a lot of people weren't vaccinated, and throughout the rest of the world, a lot of people weren't vaccinated and a lot of those who were were vaccinated with vaccines that were less effective at preventing an infection. So while Omicron is certainly infecting more people, it's not clear to me that globally the difference is all that substantial--maybe a factor of four, just guessing very roughly? It adds risk, of course, but not a huge risk.

The second factor is that rapid expansion of a viral lineage tends to result in very many variants that are all quite similar to the original, with the consequence that even if there is a mutation for increased virulence, the new variant is likely to be recognized by the immune systems of most everyone who had the old variant, so most of the potential victims will not be in significant danger (because they already had omicron). Of course, this also can go wrong in a whole host of ways, but all else being equal, broad shallow divergence is less dangerous than deep narrow divergence. Indeed, a major reason why Omicron is spreading so rapidly is precisely because it's a deep divergence and thereby evades a lot of existing immunity. (It's also incredibly infectious.)

So I don't think Omicron is, on balance, terrible news. It's mixed news: it presents both new potential dangers that you outline, but also a potential brake on an otherwise long-lasting pandemic.

Certainly it could have been much worse news: Omicron itself could have been an extra-virulent rather than a less-virulent variant.