App rejected because we ask users to signup

It's simple: You could just generate a random unique identifier on the user's device, and use that instead of asking the user to create an account. Because you could do that, you need to have actual account-based features.

More directly, the mandate is specified in the App Review Guidelines

https://developer.apple.com/app-store/review/guidelines/#minimum-functionality

(ii)If your app doesn’t include significant account-based features, let people use it without a log-in. Apps may not require users to enter personal information to function, except when directly relevant to the core functionality of the app or required by law. If your core app functionality is not related to a specific social network (e.g. Facebook, WeChat, Weibo, Twitter, etc.), you must provide access without a login or via another mechanism. Pulling basic profile information, sharing to the social network, or inviting friends to use the app are not considered core app functionality.

You should notice that that's from the Privacy section, 5.1.1.

If you've been rejected, then your app didn't demonstrate to the reviewer that you had sufficient account based features.

>APPLE demands us to allow user not to sign in to the app and browse the app.

Can we see the rejection demand verbatim, thanks.

The app has a social aspect, once we know your reccomandations we show the user the moviegoers that have the same taste and how they graded that movie. The user sees how his friends (facebook and twitter) graded and he can add/remove follower users. The user can add to his watchlist the movies he wants to see. If I generate a unique id, once he deletes the app he cant redownload the see his watchlist or recommendations.