If we're talking about the manga, then the real problem with the ending was how it completely reset Tsuna to how he was at the beginning of the series, how no one shows him any respect, and actually he's even worse than before because now he can't decide between his two love interests.
This shit really seemed like either the author left for other things or it was put on a hold, and maybe the author planned to go back, but never went back. So nothing happened. Which sucks because I really like hitman reborn it just " its done'