As you said very well .
to be honest, I never felt Mono that much into Baron until he show up out of no where and even then he mostly deny it so.....I can't say I agree. it felt empty actually much more then Mono and Lego sexual moments and it say something.
I think someone already say it before, but why can't he just move on to a new love? yeas childhood friend is importent and all but does it really have to be a romantic thing every time??
let me guess, it going to be Lego childhood friend XD yap another one. I won't be surpise at this point.
and still in the end Mono never really end up with Baron or lego so... ╮( ̄▽ ̄)╭ it left me with a bad taste.

not gonna lie, i was little bit salty with how mono x baron is canon since i'm a hard mono x lego kinda grill, but now that i've re-read the second season, i've come to realise that it kinda makes sense. the relationship that mono and lego share is definitely interesting, and i suppose, that it's the kind of couple that people would feel inclined to – the flirty, mysterious type getting together with the rash, honest type. the sexual and/or romantic tension whenever these characters interact is so enthralling.
however… idk if it's just me, but i've noticed that while mono and lego have been in sexual situations, it lacks any emotions whatsoever on mono's end. mono is extremely flirty and while you can tell that he cares about lego and finds lego attractive enough to touch him, mono likes baron in a way that i don't think he could feel towards lego. i… get the impression that mono doesn't really, and wouldn't really, wholeheartedly trust his heart with lego – but lego would wholeheartedly trust his heart to mono only for it to get broken in the end. mono's the type of character who would only give his heart to a person whom he has known long enough to freely and comfortably trust and love.
mono x baron makes sense because their relationship has depth. the both of them understand each other, as they've known each other for a very long time (i mean, they're childhood friends). baron has had a strong impact on mono's life, and mono has also had a strong impact on baron's life. mono and lego may have been in sexual situations, but it's obvious that mono's only playing around. on the other hand, with mono and baron, the creator has drawn the story in such a way that she's established a certain emotional connection between the both of them. and personally, i don't think that lego could ever understand mono in the way that baron probably does.
look, i just love lego a lot and i want my son to be happy. i hope that whoever he's going to be paired up with – it's going to be someone who will give him the love, attention, trust and happiness that he deserves.