Substantial resources? Seriously? That's a basic shell script to run a bunch of DNS resolutions and then add the addresses into an existing Firewall drop policy. That's sys/net management 100 level stuff.
You have no clue what you are talking about.
Hundreds of thousands of websites can share an IP address.
The only way to properly block a particular website is by intercepting the protocols (HTTP and HTTPS, by forcing SNI) and then permit or deny access. And that will definitely need a substantial amount of resources.