A lot of people have their disappointments with Rian Johnson's The Last Jedi. My only disappointment is that the "it's so much bigger" line from the trailer didn't make it into the film. [aside: ok, truth be told, I am also disappointed the Rey breaking up the caretaker party didn't make it into the film...and that I wish we saw more of Rey and Luke.] But that sentiment about the force is pretty much implied in the actual film dialogue (as well as why my other disappointments didn't make the film.) The Force IS so much bigger. That's the message I'm getting loud and clear in all the new Disney Star Wars films. And it's amazing.
I find it ironic that there are people who are disappointed we never get to see at his full jedi prowess. I like how many people have likened that notion of all powerful Luke as some kind of leveled up video game character. And yet we see the most powerful uses of the Force by not one, but two characters in The Last Jedi. Beside Luke's force projection, who else uses the Force in such a powerful way? Rey? No. Ben Solo? Nope. Snoke? Not. It's the other Anakin Skywalker offspring. It's Leia. Remember when Anakin wanted to stop people from dying? Perhaps indirectly he did. Through his children. Perhaps being in a family tree born out of the Force puts you one foot in the Force and one foot in the living world. Is this the reason why Anakin became a force ghost? I say yes. Otherwise, as some would argue, where did Anakin learn the trick Obi-Wan and Yoda learned? He didn't. Once he gave himself to the Force he became one. Same with Leia. You could argue Leia willed herself to live, to survive a sure death in the coldness of space. Through the force, she willed herself to live, to continue, to never give up. Or did the Force choose Leia to live as it chose Shmi Skywalker to conceive Anakin? I think it's more Leia gave herself, whether internationally or not, to the moment...and to the Force. As she could sense her son's presence, and knew harm was to come, she allowed whatever was to be. This is why I think you will see two new Force ghosts in IX. The Skywalker story will end, but Luke and Leia can live in spirit, literally, forever.