Yea there are millions of options but some of them don't work. I had serious acne as a teen, but I couldn't take accutane because I already had serious anxiety and accutane could cause depression (two kids in my high school killed themselves within a year of being on accutane- definitely not saying it's the cause but it's a factor). If Kendall already has anxiety issues then I imagine that same fear being there.
My point is sometimes you can't really treat acne without a bigger problem popping up. I know I only spoke to accutane (someone specifically mentioned that earlier), but oral medications generally fall into three categories- antibiotics, birth control, and isotrentinoin. Birth control sometimes doesn't work (mine just made me a lil chubby back in the day). The antibiotics worked super well for me, but I had a homie who had a bad allergic reaction. Personally, antibiotics took me months to adjust and caused me serious stomach distress. Isotentinion has even more obvious side effects that are very severe.
I'm not saying a model shouldn't have perfect skin, but I'm not going to sit here and blame her for her skin. I don't know her situation probably because it's a really sensitive subject.