There's a huge difference between redemption and humanization. I feel like a lot of "redemption arcs" aren't actually redemption at all, they're just attempts to humanize the villain so that they seem multi-faceted, but people read them as "redemption arcs" and think that that is meant to justify all the evil they've done before and negate whatever made them a villain in the first place. I think true "redemption arcs" are actually kind of rare because true redemption would take making the villain acknowledge their crimes, reevaluate their actions, actively choose to do better, and then proceed to make amends and become a better person, and that would this take more time than most stories are allowed to give their characters.
I've also seen people argue that a character has to be poised for redemption from the jump for it to work because once a character does something "too bad", they can't be redeemed. I completely disagree because redemption isn't justification or forgiveness, so no matter how horrible a character's actions, they could choose to become better, but because a lot of people (including writers) think redemption means "erasing the character's flaws and making it so they did nothing wrong ever", a lot of attempted "redemption arcs" just end up erasing a character's entire history or justifying every evil thing they've ever done. And yeah, in these cases, the only way to make a character go from a villain to a perfect cinnamon roll with no flaws *is* to have been planning it from the beginning and make sure they never do anything that can't be explained away later.
TLDR: real redemption arcs require a lot of self-awareness, patience, and growth, which are things that are rarely actually allocated to villains, and that's why real redemption arcs almost never get executed. The reason people think redemption arcs are overdone is because there are so many attempts to either humanize a villain that get misconstrued as redemption or attempts to blatantly erase who a character was in the name of "redemption", which is really just poor character development.
