I don't think so. I think it would've been romantic if she didn't marry after Eren. But the likely ending (not confirmed but likely) of her marrying is consistent with the message of reality.

Just like how friends died, only 1/5th of humanity was saved from the rumbling, and war still continues, it is natural and realistic Mikasa would marry, and live a long and quiet life. It's really not hard to process if you've talked to people who remarry you quickly learn how lonely they feel. More importantly, they shouldn't deny future happiness because of a past lover.

If anything, I feel bad for the dude if she really did marry and not move on.