Well I don't agree. I think he is sweet and not specifically "boring and bland". He's playful, he likes to hang out, he likes to poke fun conversationally at people (as I recall anyway, and yes this may be mostly Tom's doing). He's up for a laugh. Boring and bland is Geordi La Forge. The only time I didn't like Harry was when he sassed the Captain with his horribly cringeworthy "have you every been in love?" speech which is really his gazelle scene for me.
I agree that I didn't like when he sassed Janeway either! I thought it was totally out of character. Janeway could have been a bit more understanding of his circumstance though in that episode.
And yeah Harry isn't a bad guy at all. He just had a hard time with women. That said, he was
the one who had a fiancee back home. Tom and Chakotay didn't have that!
Well, Tuvok had his wife. But he's a somewhat "elderly" Vulcan so of course he mated already.