The weakness of the mRNA vaccine, compared to a naturally created immunity is the narrow target of the mRNA vaccines. The spike protein. The mRNA vaccines create immune system responses to the spike protein. But the covid virus is more complex than that. And it evolves. Natural immunity is created by the system reacting to the virus in totality. This does not mean the virus can’t also mutate to evade this immunity. But it would likely require more or drastic mutations.
It seems the Omicron has in fact mutated that spike protein. Which has helped it evade the mRNA vaccines more effectively. But thankfully, it also lessens the severity of the infection. The spike protein is very destructive. Early on it was noted that such a leaky vaccine as the mRNA ones would drive mutations. The vaccine does not immunize fully, but immunizes against certain aspects. It primes to fight spike proteins, but not the virus as a whole. Lessening the bad effects, but not the spread.
Natural immunity primes to fight the virus as a whole. This helps defeat reproduction of the virus in the host, not just attacking one product of it.