Oh believe me, Democrats would like nothing more than to leave all this in the past. Ignoring Trump up to a point does help deprive him of oxygen. He is a diminished force, certainly.
But, if Republicans insist on keeping Trump as their de facto leader, as we saw at CPAC 2021, and keeps making the headlines every so often and steering the Party, then there's little choice but to keep some focus on Trump. Because he's still a relevant part of the American political landscape, and MAGA is still the only practical alternative to Democratic government. 2024 is still a long time away in political terms, but the Republican Party is failing to cast him aside so it will almost certainly be Trump or a candidate firmly cast in Trump's mold.
That said, Biden keeps Trump's name out of his mouth to the greatest extent possible, which is smart, and focuses on the matters at hand. Biden and the Democrats are hard at work fixing a lot of the stuff that Trump broke.