The flu mutates more readily than COVID. With the sudden spread of COVID around the world we saw a few mutations, but the flu would mutate a lot more given the same spread. Most of us have some flu immunity though and that tends to limit spread, so it seems there are less mutations.
Right but that varies from virus to virus - the goal of a universal flu vaccine is to hit a well-conserved region of the virus which doesn't mutate much. Our inability to do it so far doesn't necessarily imply it's impossible.
Whereas most current COVID vaccines target the spike, and disappointingly the spike is a lot more malleable then hoped.
Or just that we can't stabilize/synthesize the protein usefully in a vaccine with existing techniques.
One of the big deals of mRNA is that because you get the proteins made in-vivo (in the body), you inherit all the body's machinery to do this naturally - after all, viral replication requires using that exact same machinery in order to replicate up the viral proteins in the first place.
