Polls absolutely are not the end all be all, but what would concern me if I was the Biden campaign is three things.
1) The polls seem to consistently be pointing to a Biden EC loss. In fact since the dawn of this year there have only been 3 polls that would give Biden an electoral college win on the same split as 2020. Two of them were QPAC and the other was Reuters/Ipsos which could be useless since it was only 41-37 with high undecideds. If it was only Rasmussen or Trafalgar or R internals pointing to a Trump win, then I could understand throwing them out. However, it seems like everything is pointing to close to a tie in the PV (closer to Trump+1) which is an easy win for Trump in the electoral college.
2) The polls underestimated Trump twice before. That doesn't mean they will do so this time but its worth noting. Sure they were accurate in 2018 and off in 2022, but I value the two Presidential elections with Trump rather than midterms. Even in 2022, the generic ballot which was the only national poll was fairly accurate.
3) Down ballot Dems are doing fine. This is probably the most concerning part for the Biden campaign. In 2016 and 2020 the polls were overestimating Dems across the board from the Presidency to the Senate seat to the House races and beyond. However, down ballot Democrats are doing fairly decent and arguably better than you would expect considering Biden's struggles. They have a generic ballot lead and pretty solid margins in the Senate races like AZ/NV/PA/etc. If the polls were heavily off I think we would be seeing Casey trailing, and Klobuchar with a weak lead but we are not. Casey is up 5, Rosen is up 5, Baldwin is up 7, Gallego is up 6, Brown is up 5, and Tester is up nearly 6. Meanwhile Trump is leading in all of those states, and some by big margins. If you think polls are off the same way as 2022, why are Dems doing so well in those races? The problem Biden is facing is uniquely Biden, and doesn't show up anywhere else.
Except Trump’s EC advantage has largely disappeared according to polls. Polls show Trump having modest leads in GA/AZ/NV but only marginal ones in PA/MI/WI that could easily fall in Biden’s direction if he were to narrowly win the PV, and if they do he wins 270-268.