I certainly don't mean that everyone who likes Frank or Fisk better than Elektra is sexist, or even everyone who finds her not an engaging (i.e. "boring") character is sexist. But there's an undeniable fact that we all pay more attention to men and see their accomplishments more easily, and are more readily provide extra nuanced interpretations (or headcanons) to make them more rounded characters (yes it's a fact and it's undeniable, no one needs to at me). Female characters are usually not paid attention to as much, their flaws are usually taken at face value, and people are less likely to spend time digging deeper into their characterizations to understand their flaws or to make them less two-dimensional (it doesn't help that usually male characters are better written and given better lines than female characters, so it's even easier to dismiss female characters). I never mean people aren't allowed to like male characters more, but I think we should take time to examine whether the fact that a character is a man raises our opinion of him, or vice versus, whether the fact that a character is a woman makes us pay less attention to her.
The straight-up "she's boring but it has nothing to do with sexism" and the unprompted opinion about fictional romantic relationships are like parody and make me assume that post was sarcasm anyway.