The flu vaccine isn't incredibly effective compared to some of our better vaccines, but its benefits certainly outweigh the risks, even in the worst years.
One of the arguments I saw in this thread was that many have already been exposed to COVID and thus the second wave after reopening wouldn't be nearly as bad. The worst hit place in the US is NYC (by a large margin), and random sampling suggests that 20% of NYC residents have antibodies. If I'm not mistaken, 15-20% effectiveness of the flu vaccine is considered an exceptionally bad year. Think about that for a second. Imagine if we got to this level of immunity from one lousy vaccine given to the whole country without having to shut down economies and overwhelm hospitals.
That's why I'm for flu vaccines even in the worst years. Also, we don't know it's a bad year for the vaccine until after the fact anyway.