Once the MC gets tranformed into a girl, he becomes a completely different character, and not just physically. He becomes just as unlikeable and frustrating as the girl he turns into.
MC starts off as a strong willed character with clear goals and determination. He pushed the plot forward and could influence the world around him. But now he's a pathetic aimless character who instead gets pushed around by the plot and other lesser characters. For example: the only reason he starts training again isn't because of a personal drive to become strong (he surely must have been that way to become as strong as he is in the beginning). it's actually cause some random old bumfuck fortuneteller basically told him "yo, you wuz strong n shit. so why dun you just start training again bro!".
You can pull off a stunt like depowering your MC, but it'll only work if you actually keep his character intact. And if you cant do that, at least write him as the underdog. The MC, as he is in ch 48, is NOT an underdog. He's a little punk bitch who get pushed around by so much as a breeze. weak != underdog, An underdog is a character you root for, Someone who wins you over with their strong drive and determination. MC has neither. All he has is "ok lets do this over again and get strong cause some old geezer told me, lul"
tldr: the author basically killed off the MC and replaced him with a lesser character. and also fuck the author for making me write up this pointless complaint