> Think of it as trying to do for WhatsApp what Resend did for email or Stripe did for payments

If you were a PM, you should be able to see what is wrong with this statement. You are trying to do for a specific product what your examples did for more generic needs. You are 100% dependent on the success of WhatsApp, which ultimately puts you in less control of the success of your product, not more. And that sounds like it is in direct conflict with the reason you left your cushy PM role.