Lexi's problem, to me at least, is not what she did, but what is going around her.
Actually, it's not a problem, it's just why she fails to interest me:
Layla has whole Elena baggage around, not to mention ASP, initial Alexis route and so on.
Erynn has by far most interesting story arc.
Iris shows out of nowhere and is big wrecking ball capable of ruining relationships.
Nikki and Cara are far away, so mostly out of picture.
Meanwhile Alexis has almost nothing major to her relationship.
Sure, it starts kind of rocky due to whole Erynn lying part, but after that, it's smooth sailing unless you actively cheat.
Her path is smoothest possible if player is not cheating.
Every other girl has some wrench thrown at them, Alexis doesn't.
That makes her perfect girlfriend, but really not that much fun (personal opinion) as a route.
Metric fuckton of content though.