These are essentially new characters, with traces of the old. The relaunch has firmly been placed in the "hard reboot" category. Same as the Golden-Silver Age transition.
In a world where: Bruce had his paralysis cured, the JL leader returned from the dead, was cloned, and Lex Luthor was cloned, and Damian had his paralysis cured, Jason had several injuries repaired, John Stewart had his paralysis cured and knows every wizard who's anyone can't have her own paralysis cured within a short period of time? Seems legit.
Turning her into Batgirl again actually makes sense in the context of the DCU. Plus she still did her time as Oracle, just streamlined.
Giving him a relationship with a woman other than the one he has been with for the past 25 years in going backwards? Seems to me it would provide fresh stories for writers to work with instead of what we've seen because Superman and Lois will never grow old together, because that's not the nature of any ongoing medium.
Why? It's providing writers with fresh material and readers with fresh storylines, relationships and paradigms. The whole point of a reboot.
Would you complain if a film reboot (let's say Batfleck) required you know about TDKR, and Bruce's retirement with Selena, despite being a reboot?
Not all undone.
Subjective, not a lot has changed about her core other than her being more sexually active with the person she's in a relationship with.
Batwoman has only had her own ongoing in the New 52.
They're trying to develop Barry Allen, who had his big sendoff ruined in 1986 and then didn't appear for over 20 years. Then they can introduce a brand new Wally West and develop him, independently from Barry, which is something his character sorely needs in order to not be defined as the "successor Flash" or "other Flash".
I'd agree, if it weren't for all the differences. Cyborg got a push, MM got his own JLA book, Steve Trevor got a push, Shazam got a push, Aquaman is bigger than ever, Nightwing is undergoing a big shift in his own status quo. The current DCU is vastly different to the end of the Silver Age.