Dealing with 4.3(a) rejections can be frustrating. Since you've already made technical changes without success, I'd recommend escalating to the App Review Board detailing your uniqueness or added value. They may be able to provide clearer guidance on exactly what needs to change to meet the guidelines. You can request an App Review Board review directly in App Store Connect under the Submit an Appeal option.
Topic:
App Store Distribution & Marketing
SubTopic:
App Review
Tags: