Yes, that is correct, almost no need to manually add blocked domains anymore. Besides the standard disposable email providers (like Mailinator) Kickbox also catches a lot of the dynamically created disposable emails.
Of course, there are paid services like https://debounce.io/ and https://www.ipqualityscore.com/ which are even better, but I wanted to ship the plugin with a free service out of the box.
As mentioned in my OP, you could still use the plugin and relay the response from a paid service to one the plugin understands e.g. via Zapier & co.