Meh. Biden is still very popular - right now. Also, those numbers reflect the polarization/partisanship of the times.
According to that Gallup poll, Biden is just as popular as Obama was with independents at the same point and more popular with Democrats. The 11% approval of Biden from Republicans should be expected lol - most Republican voters believe that the election was "rigged/stolen".
Finally, Gallup honestly isn't the gold standard of polling as it once was