That would be great, but it appears the immune system does not work that way:
> the body's immune system ... preferentially utilize(s) immunological memory based on a previous infection when a second slightly different version of that foreign pathogen (e.g. a virus or bacterium) is encountered. This leaves the immune system "trapped" by the first response it has made to each antigen, and unable to mount potentially more effective responses during subsequent infections.
That speculation has only come from people who don't know what they're talking about.
Is there any other virus where this happened? It didn't happen for smallpox, ebola, measles, flu.
You're also ignoring the law of big numbers: if it kills fewer people than delta but infects more people we're probably going to see more deaths. People won't want to take any precautions against it, which means very many more people will get infected.
Personally I don't mind sitting inside again for 2-3 weeks while this all gets figured out, but I know I'm in the vast minority by this point.
The mildness of the symptoms is just as newsworthy as the fact that there are breakthrough infections. It has long been speculated that COVID-19 would evolve into more contagious but less virulent variants. Omicron may be one such variant. If it is, that's probably a good thing.
Wouldn't it be great if a vaccinated person could get omicron, have a mild illness, and then have even stronger immunity against other variants?