It's that much less across all age groups, so there's even less benefit for the demographics not at risk. Plus for the past decade or so the overall efficacy has dropped even further, floating around 30-40%.
On top of that, vaccines need >50% efficacy to get approval. If the flu vaccine was invented today, it wouldn't pass.
Why is 50% less flu not a good thing?
This is like the sterilising argument about the Covid vaccine. It’s somehow damning for the Covid jab but not for polio.