Why people hate what gohan become? Like seriously, when bulma and others met gohan and bulma ask gohan what he wants to become he said he wants to become a orthepedus, i dont even know what that is back then but he dreams to become that. And ever since then gohan hates violence but he wants to help people and his friends, he was force to fight, until the whole series of cell, all he wants is to protect his friends and family. I just realize this when cell trying to provoke him and i dont hate what he become, he still helps people in a way.
I personally don't mind it, but before Super, even at the end of Z he was confirmed by Toriyama to be the strongest character without fusion on more than one occasion. So to see him fall down the power rankings in each saga of Super it pisses some fans off.
By the start of Battle of Gods, it's debatable if Goku and Beerus surpassed him in power. (Goku was beaten in 1 blow vs Gohan 2 or 3 by Beerus)
Midway through Battle of Gods Vegeta's Rage Boost clearly put him past Gohan, because he did more damage.
End of Battle of Gods, Goku got God Mode
RoF arc, Gohan couldn't even go Mystic anymore and while stronger than the others, he was one shotted by base form Frieza.
Champa Arc, Gohan was a non factor.