I know i don't fucking care about nisekoi or domestic kanojo ending, because i don't interest to read them. But, this time, i never this disappointed to know that the series that i interest end in this kind of way.
Japanese authors all seem incapable of writing endings. Probably a culture of "keep writing until told to stop", so because the author was told this was the last volume he just crammed everything important in it all at once instead of spreading things out properly.
The ending you described sound lame. Maybe I should drop this but on the other side in manga thinks started look interesting. Most probably I will read this until things will start looking bad.
I can't disagree with your statement because I saw this many time when I read some japanese things long enough. Authors stop trying care about things like story consistence, characteristic and development of their characters or established by them (by them I mean the authors themself) message of the story.
In some way that also apply to TV series which have imposed in advance number of episodes per season.
if that's the entirety of the end then geez but personally I got more investment in the worlds and conflicts than the romance so if those are good I've got no problem continuing