Soap-opera-ish is completely right - killing off a character is meaningless if you establish your writers will stoop to a fakeout or a never before mentioned sibling/twin (or clone or mirror universe version, since it’s sci-fi).
Okay, but that's not really what they did with Sela.
Sela wasn't 'Tasha returned' - she had nothing in common with Tasha (in terms of personality or her role in the show) except for being played by the same actress. She clearly wasn't just a backdoor soap opera route for Tasha to return.
Also she was only actually in four episodes (on the first of which the character wasn't identified and Denise Crosby was an uncredited voice only). Sela's brief appearances were so memorable that we tend to forget how minor her role actually was across the span of TNG - Tomalak had a bigger role, for example.
Definitely all true. But the implication that she was made into a Romulan love slave, especially after having established her backstory always rubbed me the wrong way.