Quote - At what point has a character been changed enough to become something completely different?

The characters have always changed, and not just tweaks in the costume. Take one of the most iconic: what do we think of Batman (in the comics) these days?

Doesn't use a gun. Doesn't kill (however much someone might deserve it). If Batman picks up a gun and shoots to kill, the situation is one so dire that the only choice of him not shooting to kill is literally the end of the world. There's a reason why "Batman Grabs a Gun" is the trope describing a situation so bad the guy who doesn't use guns has to.

In Batman's first few appearances in 1939 and 1940, he had no problem plugging the bad guy. He changed over time.

These days, the humourless crazy-prepared detective who doesn't trust anyone. In the 1950s and 1960s (and the TV series), cheerful goodball who made bad puns while hanging out with Superman for laughs.

Even in the civilian identity: Bruce Wayne, rich idiot with no day job versus the more modern Bruce Wayne, multibillionaire businessman who is very good at what he does.

Superman for quite some time was the real identity while clumsy Clark Kent was the disguise. His friends who knew both identities called him "Superman" or "Kal-El". For years now Pulitzer Prize-winning journalist and smalltown boy made good Clark Kent is the real person while Superman is what he's called in costume. His friends who know both his identities call him "Clark".

So why should Diana/Wonder Woman be any different?