Just for perspective.
The original vaccine came out in 2020 and stayed the same until 2022, when the Omicron variant (34 mutations) was added.
2023 saw another vaccine that added an additional 17 mutations, followed by the latest 2024-2020 "XB-2" formulation that has added an additional 38 mutations to all the previous formulations.
So it seems that the vaccines are reconfigured on a roughly annual basis.

To answer your specific question, I don't believe that we have LC because we keep catching new variants! Hopefully you are keeping your vaccinations up to date, and using appropriate cautions when out-and-about.
There are many, many studies ongoing about LC, and we are hopefully awaiting some definitive conclusions and, hopefully, remedies before too long.
My personal suspicion/theory is that we have an ongoing, post-viral heightened immune response/reaction and resultant inflammation, sustained long after the initial (acute) infection has passed, so the current configuration of the circulating virus might not be all that relevant, (if that makes sense... doubt it...)