As someone who used to often play dating simulators and still occasionally plays them, i adore this game for what it is. Most dating sims that i played are really illogical, contrived, and cliche. This game may be slightly poking fun at those games, and the players, but imo it does it in a charming way. I don't see it as rude, not at all - especially the Zaine ending. It's like 'go on, go and actually meet people, actually experience love but in real life, not just in a game.'
I don't know what games you play. Most of the dating games you play you're spending three years or several months getting to know a character before you so much as fall in love, much less get married. There are shorter stories (usually on mobile games) but it generally involves magic or other such circumstances that allow easier and quicker love. And more importantly, it's fiction. Do you walk up to a person and lecture them about how they need to get out and experience 'love' in real life when you see them watching a romcom or reading a romance? Probably not, unless you're a presumptuous dick. Do you go up to someone who plays Call of Duty or Skyrim and say "Hey, you should join the military for real" or "why not learn to be a real outdoorsman and find adventure in real life"? I bet you would not do that. Yet, somehow it's an acceptable target when it's a dating sim. It's okay that Call of Duty and Skyrim aren't realistic, that you can jump off a mountain and get shot in the chest several times and shake it off, but fall in love with some prince in thirty days?! Preposterous! You need to get a life and stop wasting it playing games!
It's absurd and it's uncalled for. How a person chooses to enjoy themselves doesn't say anything about what they do in real life. Good lord, married people play dating sims because they're fun. Or they would be, if this game didn't do its best to suck all the fun out of it that it can.
And I get it, it can be fun to poke fun at dating games (like any genre). That's why Haotoful Boyfriend is so popular. The trouble is, this game doesn't do that well. Even the author themselves state that they started to do that and then got lazy. And it shows. And when it's lazy and your reward for finishing a route is a pretentious lecture, it just comes off as rude, not funny.
I'm sure there are people who enjoy it, but to me everything I've seen in the game and by the author on their Tumblr all I see is someone who thinks playing dating games are something to be ashamed of and discouraged.