The whole “married with kids” ending wouldn’t even be so bad if there was actual romantic development with the endgame couples. But coupling some popular ships, usually where only the woman expressed her love, and letting the fans make this cobweb of every moment that can pass as romantic is unfair. It’s not our job to pinpoint when they might’ve started falling in love. Show some flirting, a proposal, a kiss or something.
Learn from Fullmetal Alchemist!!! It’s the perfect example of shonen manga nailing the “married with kids” ending!