a URL is also a single string that's easy to copy and paste, the question I have is how these strings get resolved to something that I can connect to

if you need to go thru a relay to do resolution, and relays are specified in terms of DNS names, then that's not much different than just a plain URL

if the string embeds direct IPs then that's great, but IPs are ephemeral, so the string isn't gonna be stable (for users) over time, and therefore isn't really useful as an identifier for end users

if the string represents some value that resolves to different IPs over time (like a DNS entry) but can be resolved via different channels (like thru a relay, or via a blockchain, or over mdns, or whatever) then that string only has meaning in the context of how (and when) it was resolved -- if you share "abcd" with alice and bob, but alice resolves it according to one relay system, and bob resolves it according to mdns, they will get totally different results. so then what purpose does that string serve?