WhatsApp needs to improve this things:

• Other systems, like as Telegram (Example Broadcasting channels), Hike (Example Hike Land), and Snapchat (Self-destructing messages, Lenses, and other features), are evolving at a much faster rate.
• Leaks personal information: Group member listings reveal users' phone numbers.
• There is no in-app browser to see the app's content.
  
• The number of members in a WhatsApp group is limited at 256. (vs. telegram of 200K).
• Characteristics of Generation Z: Lack of self-destructing messages, interesting Snapchat-like filters, poll/quiz creation, Snapchat-like animated stickers, and Telegram, which are all appealing to Generation Z. (While animated stickers have launched on WhatsApp, they are no match to telegram stickers IMHO).
• Document Size: You can only attach files up to 100MB in size (vs. 2GB in telegram

Read More: How to hide last seen on Whatsapp