There's nothing wrong with starting your next game while you're still finishing or even fixing the current one. Most developers work on 2 or more games at a time. In this case, they're still keeping a team working on BF2042 while another works on the next BF.
What was probably a bad decision was to announce this while people were still upset over the state of BF2042. They could've maybe learned something from CDPR, of all developers. Notice that they announced their next Witcher a few weeks after their long-promised next-gen update for CP2077. I imagine that they've been working on the next Witcher for the last year, but knew better than to announce it before CP2077 was in better shape. They're not abandoning CP2077, though, since they're keeping a team working on its expansion DLC while another works on The Witcher. It's likely the same thing here.
I don't want to sound like I'm defending DICE, though. Making what seems like a bad decision to announce this now makes me question if they really learned many "valuable lessons."