I don't think ignoring something that happened before is screwing up the work of the writer who wrote that. The work is still there, it can still be enjoyed. Ideally (in an utopic DC Comics) if a writer wants to ignore what goes before, he does it. If the writer after that one choses to re-integrate the ignored stuff and ignore the work of the previous writer instead, he can do so too. If someone after that has a way to integrate everything, he can do so too.
What some continuity obsessed people (Moty) fail to see is that their opinion is as valid as any other opinion. Some like continuity, some don't (I think I'm between those two). Why should the people who like continuity be taken into consideration when the comics are made and not the ones who don't like it? Why can't both be taken into consideration?
