It's pretty generic. Standard isekai+wilderness growth+kingdom building type thing. You know, all those where the MC gets a tool of some kind to build his slow life BS. Gains a harem, does nothing, etc. The only 'twist' is that he's marked with a blessing that the main church calls an Evil God or something, which he knows nothing about. So he was kidnapped away from his father (a High Priest of that very same religion) and adopted twin sister without being able to say anything.
Anyway, it was pretty standard, where he initially was able to escape from the island, when he realized that OTHER 12 year old children could be dumped there every year, so he decides to stay and cultivate the island so that future kids won't die. Then he saves a princess and a few slaves from a losing country on a shopping trip, then later on a village of bird-people who were abused and manipulated by a 'corrupt' bishop of the same religion as the beginning.
Anyway, it was decent, but the problem is that ANYTIME the MC gets involved with others, he... wusses out. When he's got no power and is fighting a giant monster with a stick, great, that makes sense. But he has a high powered combat android mage, a foxgirl who's a badass fire mage, several others with powers (either blessings or magic) and he... takes the absolute lamest route possible every time.
The bird people? Well the village they were near had been lied to by the bishop, and so they had an unreasonable fear and hatred of the bird people. All the female birdpeople were captured and locked up, while the men were treated as slaves, and were about to be killed and disposed of. So what does the MC do? He takes them to a protest.
...like a walk in the streets with posters protest. What. The worst part is that when it obviously doesn't work, what does he do? Uses violence and force to break into the place where the female bird people are stored. Welp, good job!
There are MANY times when they're attacked by people who are ready and willing to kill them, and at no point does the MC ever do anything in return. And when it's brought up that he's being pathetic, he remarks that he KNOWS this world isn't a kind place, but he's 'not ready' [to kill people].
There's also teh fact that the MC has a ready and willing harem - no joke, the princess actively wants to have an Heir with him, and he does nothing. Despite knowing that people around him love him, and he feels the same way, he doesn't like doing anything but hugging his android. Admittedly he's 15 by now in the story, so he's a bit young by our standards, but definitely not by that world, as evidenced by the princess character. But the main thing is that he's a reincarnated person (Japanese, of course), so he's actually a 35 year old - and yes, he had his memories from when he was a baby, which is fortunately not shown much. Hate the stupid 'superpowered baby' trope. So the fact he's 15 really doesn't matter at all, not physically (started puberty no doubt long ago), not socially (again, not out of the ordinary in that world), and not emotionally (he's 35). By all rights of both worlds he shouldn't be that pathetic.
So yeah, basically it was a generic slow life story, but then the author wanted to put in some action, but did it poorly, and it's really hampered by the pathetic and lame MC, both in terms of action and romance.