Literally the whole point of Luke showing up and making a scene is inspiring hope across the galaxy.
“The Rebellion is reborn today.”
The Resistance won’t be able to fit on the Falcon for long. This is made pretty clear in the film.
Yeah, but that all depends how the FO will rule the galaxy. It’s not two major organisations backed by various systems like in the OT. In ANH many systems were rebelling against the Empire, because it was oppressing the galaxy. At the end of TLJ the galaxy had apparently accepted the FO’s rule. Nobody answered the Resistance call for support. Now it’s literally hundreds of thousands of troops versus fifty people. If the FO are smart, there won’t be a Resistance ever again. They won, and it’s up to them to let it slip through their fingers. The remaining Resistance members have no part to play, but wait, and hope they screw up.