Structurally they are similar enough that we can communicate. The discovery would be altering our science, but every attempt to exchange beyond technicalities and niceties is somehow incredibly boring to both sides.
After the initial awe, it would be like, yeah, we know aliens.
Unless we have a way around general relativity, boring will describe any conservation with another civilization.
Hello.
wait 1000 years
Hi. How are you?
wait 1000 years
Who the fuck are these guys?
Space is really, really, really big. And by comparison any form of communication we have yet discovered is very slow.