They don't release Android apps, therefore you still need to use Venmo and Cash App if you want to send money to someone. So people aren't going to use this over Venmo, Cash App or PayPal.
Google Pay supports iOS which is why it used over Apple Pay in countries where iPhones aren't the dominate mobile OS.
I mean... I singlehandedly disprove your claim. I use Apple Cash very frequently, even in cases where both parties have other apps on their phones. IMO they don't need to remove Venmo or Cash App from the market in order to have a meaningful product that adds value for their customers.
Google Pay supports iOS which is why it used over Apple Pay in countries where iPhones aren't the dominate mobile OS.