I answered this question on the first page! In the game, (if you play it), it becomes clear that you can skip it if you are not interested in sissification and transgender people.
The issue with Kenny isn't about the sissification or transgender aspect of their plotline. It's one thing to make Kenny start wearing women's clothes as a punishment for something to start with, but there's no way to tell if Kenny is actually transgender or if they're just continuing to wear women's clothes because they're being forced to do so by the MC. So even if a player were into the transgender/sissification aspect of Kenny's storyline, it very quickly becomes uncomfortable because there's no indication of Kenny being into it or even passively accepting of it, as most indications are that Kenny is only going along with it because they're scared of MC, who is taking the punishment aspect of Kenny's crossdressing to a psychotic level. Every instance of Kenny indicating that they're enjoying wearing women's clothes has been under threat of even further (and implied more embarassing/violent) punishment(s) from MC. Having the dev of the game confirm that this route of so far exclusively nonconsensual content will definitely lead to sex with the character throws huge red flags for anyone who doesn't have a rape fetish. The super inconsistent gendering, while probably simply a translation error and unintentional, also makes the route confusing because there's no clear indication whether Kenny nor MC consider what is happening to Kenny simply crossdressing or actually transitioning.
I don't think the complaints about Kenny's route are about the route's mere existence. The route has a very clear option to opt in or out, so most of the people who are complaining are probably people who opted into the sissification route and are very put off by how over the top MC's abuse of Kenny is on the route. The assumption that people who were into sissification content would also definitely be into nonconsensual content was misguided at best. Also, the context that the MC may be forcing Kenny into a transition in an environment where many of the characters are depicted as very transphobic makes how abusive MC is toward Kenny and the fact that MC may be forcing Kenny into a life where they will also be abused by the rest of their family because of what MC is forcing them to do even more unsettling.
I think Kenny's route would be much improved by either removing the nonconsensual content altogether, or at least adding an option to stop punishing Kenny, but finding out that Kenny has enjoyed being sissified and is interested in transitioning and exploring that with her. Removing the family's transphobic and homophobic comments and making them more accepting of what they should be perceiving as entirely Kenny's choices would go a long way to making Kenny's route seem less abusive. Fixing the gendering issues to make it much clearer whether Kenny is really transitioning or just crossdressing would also be helpful because it will matter to some players whether they're feminising and hooking up with a crossdresser or a trans girl.