I was also dissapointed with a camera app o w10 mobile on my lumia 640 xl. What I did was I rolled back to 8.1 and did a hard reset and installed everything fresh like when I bough a phone (I didn't remove anything from SD card, just from phone)...and after that I updated back again to w10 mobile and repeated everything, I did a hard reset and I installed everythig from scratch. I also installed lumia camera app, a USABLE one. It'a a bit slower than camera app that comes with w10 but the pictures are much better. Just be sure to turn off automatic app update in the store because I'm not sure what will happen if lumia camera app get updated...I have an offer in the store to update lumia camera app and windows camera but for now I'm not updating because I'm afraid that lumia camera app will become unusable... :straight: It took me a lot of time to do all of this but it was worth it because I now have better camera app (in my opinnion) and new w10 software... :amaze:
Good luck!