I'm not sure what you mean, what sounds dangerous to me is not caring about what services are listening to on a server.

The firewall is there as a safeguard in case a service is temporarily misconfigured, it should certainly not be the only thing standing between your services and the internet.

If you're at a point where you are exposing services to the internet but you don't know what you're doing you need to stop. Choosing what interface to listen on is one of the first configuration options in pretty much everything, if you're putting in 0.0.0.0 because that's what you read on some random blogspam "tutorial" then you are nowhere near qualified to have a machine exposed to the internet.