Oops, I read that wrong
Excuse my final exam syndrome.
The thing is, I think it's nearly impossible to act like most of the events in TASM2 never happened. The reason is because so many things
did happen, and they involved major characters.
Harry wasn't done as well as they could have utilized Dane, and Cooper's Norman has been wasted until they prove us otherwise. TASM2 cemented that Oscorp has bad intentions and is being overrun by corruption - how can they undo that? Maybe they can go back to Peter's search for Ben's killer or try to find something from the end of TASM1 to continue from, but there's not much else besides Peter and Gwen's relationship (and now Gwen is gone).
Additionally, not mentioning Ben in TASM2 was a buzzkill, so to drag that plot-line out of the closet now would feel forced and awkward.
I wish they had handled some of these elements of TASM2 so much better. Gwen's death is the perfect opportunity to introduce a new story, but some of the muck that was created in TASM2 will inevitably be dragged into TASM3.
They shot themselves in the foot and now they have to deal with it.