Is using a VPN with messenger services like Whatsapp completely useless?

Am I right in assuming as Whatsapp is linked to your phone number that using a VPN does virtually nothing to protect/hide conversations on it?

Does it stop someone peering into my conversations? Is there any element of security that it provides? Or are my conversations just as vulnerable as the average Jo?

The conversations are end to end encrypted anyways. The only advantage I see is, that you ISP can’t see what messenger you are using. WhatsApp has your phone number anyways, as you said.