So, i recently started reading novels in this genre (both translated and original, i.e. the kind you can find on RR) and after a while i realized that aside from Mushoku Tensei none of the ones i read so far have been translated/written up to the point where the MC finally gets over his childhood/early teens. Any suggestions?
You won't find many japanes novel where the protagonist grow beyond his teen years. The protagonist has to be a teenager for the whole story. Only when the story is done can he be a true man (or even a geezer)... In the epilogue. Interesting things happen only during the teens age (or before). After, it just becomes slice of life with wife and children and happy ever after; And fictions about reincarnation you find on RR and other sites tend to follow the same rule.
The Japanese WN I'm translating starts its main story with the reincarnated man already grown up. Unfortunately, I haven't translated anything beyond prologue. Hahaha
Theoretically speaking the MCs from ATG, TDG, CSG, MGS, OEM, PMG have all gone past their teenage years, some of them even to the point of being adults or extremely old. But of course, that's before their reincarnation. But they will eventually grow up, it's just that there aren't enough translated chapters yet.