It's not the worst... but also not great. If you're able to set aside issues with the baffling lack of common sense for the premise, it's a sort of fluffy air-headed manga good for wasting some time. I can only guess that the high rating is due to the art for the receptionist, the cute dragon child, and maybe the "comedy"?
The main issue is that the story tries to portray his love as comedic and awkward, but it just comes across as delusional and creepy. He's spent 10 years fantasizing how his married life with her would be like, and gone way, way overboard with what he's purchased for his future wife (and their children)...But he's put no effort into actually getting to know her on his own. It takes a secondary character telling him outright hints, plus very obvious plot meddling from the author in order to get any progression.
If we ignore his delusions he's outwardly respectable, as the one thing going for him is that he doesn't hesitate to help other people.
In reality, his delusions and obsessive gift collections are way more likely to freak out the girl of his affections. But as this is a manga, she obviously likes him back, and the plot is actively pushing them together, so lucky for him that hurdle is cleared preemptively.