Well if the US and other western countries got fully behind with End to End encryption without backdoors, eavesdropping would be no issue. Instead they are trying to force "backdoors" into encryption people already use.
The cable is point to point. (Well ok there is branching but let's ignore that) So you know those two endpoints are talking. Not about what.
And this is trivial to bypass by always sending, regardless of whether there is data to send. Just fill the cable with dummy packets.
Unless you compromise the keys used on either end you learn absolutely nothing by watching the cable.
And then it took us three or four major iterations of HTTPS before we stopped revealing a bunch of metadata about the question you're asking the server.
Also if you know what service I'm talking to, and you know anything about me, you can get some statistically relevant information from the traffic patterns. You might be able to tell if I'm using a chat application, or watching videos. And if I'm being surveilled by state actors, then the fact that I'm chatting might suggest what I'm getting up to.
I'll get back to you (possibly).
Capture is performed and encrypted data is stored, waiting for quantum computers to be available and cheap to then break in the future what we exchanged securely today. It counts on having the half life of data greater than the average time for quantum computers to arrive.
Post quantum cryptography algorithms exist (PQC) and some open source implementations are there. Even for SSH. and NIST has an active crypto challenge on that.