If people actually wore masks and got vaccinated we could have eradicated

Not really, there was no chance of us eradicating covid. Covid spreads well even among the masked and the vaccinated. We could only slow it down.

but now it's like the flu where it changes to quickly to manage

It was like that from the start, there were multiple competing strains of covid right from when it was first discovered since it had already been spreading for at least 2 months at that point and was all over the world.

Covid was always going to become endemic.