Other people's products are patented in appearance. Can I apply for a patent on their appearance after making some changes?

You can definitely apply, but you may not get a certificate. If it is only slightly changed, it is a bit doubtful whether this appearance can be certified. The appearance is reviewed by acquaintances. If you are familiar with others, you will basically be rejected; Even if the examiner doesn't find someone else's appearance patent and gives you a certificate, the patent right is unstable. If you encounter a lawsuit or something, it will easily be invalidated-all the above individuals understand that they don't know much about patents, but they are just apprentices in the agency.