I like this but it falls into the same trap that I notice in a lot of other isekais that just bothers me, in this case the guy has a legendary unbeatable spaceship and a mecha specifically designed to overpower magical opponents, to put it mildly he's got a nuclear arsenal in his hands while the rest of the world has ballistic missiles. He has this immense world-changing power and he doesn't think for a single second about changing his role in society or changing the storyline or fighting against the roles imposed upon him by their society, he'd much rather wallow in self-pity and accept the fact he doesn't deserve his own ambitions or happiness.
In fact his active goal was to get married to a nice decently attractive girl and live out his life supporting his spouse and her many lovers, the alternative being stripped of all titles and nobility so he can make a living off his island and not be forced to marry a horrible fat noble girl that will treat him like trash.
Even when presented with 2 amazing girls that do genuinely like him and treat him well he doesn't look at either as a woman he could love because their status and nobility is too different...
Again, he has the power to wipe out the kingdom, if not the entire planet, and he's bowing to societal norms/hierarchy because 'well what can I do to change this', like are you kidding me? This is like if One-Punchman was in a feudal fantasy world and instead of just punching everyone that opposed him and making his dream a reality he instead just farmed mud in a ditch because he wasn't born with noble standing, it's so fucking annoying! Do your own thing! Who is going to stop you? The Kingdom? Go somewhere else, if they want to stop you too then blow them up! Make your own Kingdom! Maybe travel the stars to find a new world to colonize! Hell, why not just live out over the ocean in your untouchable space ship and do mercenary work while living with a harem of beautiful slave girls?!
"I don't want to rock the boat, I better just accept a life of simple misery, it's not like I can change the world."
HE SAYS WHILE HAVING ACCESS TO THE SINGLE MOST ADVANCED PIECE OF WEAPONRY TO EVER EXIST!