Why can’t I add cards to wallet and also Apple Pay cannot be setup on my iPhone 11 Pro in India

As you can see here, Apple Pay is not supported in India.

Countries and regions that support Apple Pay - Apple Support

See -> About billing for Apple subscriptions and media products in India

About billing for Apple subscriptions and media products in India - Apple Support

India

•           Apple ID balance (from adding funds)

•           Net Banking (adding funds only)

•           UPI (adding funds only)

You can use / pay with your Apple ID balance, see: Add money to your Apple ID balance

Add money to your Apple ID balance - Apple Support (IN)