Some background: for many years, the flu vaccine has had what's called the "egg problem". The vaccine is cultivated in chicken eggs in a sterile environment. The US government pays billions every year to maintain these production lines. It takes about 4-5 months to go from choosing what flu strainsa are likely to be prevalent to there being a vaccine. The production line can't scale up quickly either.
Also, people who are allergic eggs can't generally take the flu vaccine. That's why they ask you.
For decades the US government has funded research to get away from this system and that resulted in the mRNA vaccine. It doesn't require chicken eggs to produce and the lead time for producing a vaccine goes to almost immediate. we saw this with Covid where the candidate vaccines were produced in days. This fed into conspiracy theories about it being unsafe because it was rushed but it was nothing more than the culmination of decades of research where fast vaccine turnaround was the entire point.
In future years we'll see mRNA vaccines turned to diseases that have thus far we've been unable to produce vaccines for.