I believe as we're mostly NATO then militarily we will be sharing, but its a fact we dropped out of the centralised system, that has weakened us both as there is now a level of red tape that wasn't there before.
As for the Dutch, Italian and Germans point you actually proving the point being made and just don't seem to see it. the UK being in that shared system would make the EU stronger as we would be sharing gas supplies, they have the capacity to store it which we dont, we have the supplies that they dont. in the shared system we would have been piping the large glut of gas we had over summer into there storage areas for distribution where needed in winter. including to us as we dont have the storage we need anymore and cant produce enough to supply our own needs in real time. ( because of being in that shared system we closed down the storage units as they were not needed anymore ).
there really is no denying it, Brexit made us, and the EU weaker than less capable of handling systemic shocks like this than we could together.