At the time, it was not at all clear that in-orbit rendezvous would be feasible. One of the reasons this is so important is that it enabled lunar orbit rendezvous.
This drastically reduced the total launch mass for the Apollo missions.
I celebrated when I made my first rendezvous in Kerbal Space Program. It's not easy to do and knowing that it was done in real life with tougher constraints was awe-inspiring.