Embeds are fetched and displayed without user interaction.

This also assumes the admins always use a single network with a single static IP address.

Not really. Send a DM to every single admin of an instance and wait until you get enough collected IP addresses. Pay someone running a botnet to flood those addresses for an hour or two.

Even with a dynamic IP address, you're still stuck with it for a while. If you're lucky, power cycling will get a new one immediately. If you're not you get to enjoy waiting for a day or sitting on hold with your ISP's support number, running through their scripted support process until you finally get to someone capable of helping.