Rey meeting Luke to train with him is the conclusion to the main plot of finding Luke and Rey’s own character arc in the film. There is a “to be continued” in that we know there’s more story that will be told but this is still 100% an ending to the story that the film is telling.

In an earlier draft of the script they found Luke about 2/3 of the way in but they realized once Luke showed up it became his movie. They needed this film without him to establish the new characters and how Star Wars is no longer Luke’s story, it’s Rey’s (though of course they intertwine).

Luke not speaking at the end is a matter of “can’t please everyone.” If he talked, a lot of people wouldn’t be happy (myself included). Star Wars endings are dialogue-less, remember? He didn’t need to say anything anyway when his face was already saying so much.