That is a good point. I am unvaccinated and am concerned about that issue. I have had Omicron and have a high level of protection. A new report form the US CDC confirms that natural immunity provides a high level of protection.
I'm afraid that's not correct. Many people are getting re-infected over and over again with this virus. People have reported being sick with both the first wave, Delta and Omicron. As soon as the next variant emerges, you will have little protection. The immune system doesn't memorize coronaviruses as well as, say, herpesviruses, which is why we get sick with cold virus variants every winter. This is also why the vaccine effect wanes over time, but same is true for natural immunity.
It has also been shown that depending on the strength of the infection and immune response, individuals might produce very different levels of antibodies. So if you had an infection with less symptoms, unfortunately there's a chance your immunity won't last as long.