Well again, ask voters if the president is competent, and you are always going to get a result close to 50/50. And those results will go up and down as crises come and go. When the economy gets full steam and the covid cases drop off, and the Afghanistan debacle falls into the past, the fickle americans will poll differently.
Even now in a time of crisis, Biden's aggregate numbers are not as low as Trump's peak approval numbers. So at the low point of the Biden presidency, he is still polling better than Trump at the best point of Trump's term. Which seems about right, given the results of the last election.