There are some Force ghosts in The Rise of Skywalker. We get Luke on Ahch-To when Rey crashes the tie fighter there to live in exile. We also get the Skywalker siblings at the very end of the film looking at Rey as she takes their family name as her own. Those were all great moments in the movie but there could’ve been so many more.
During the final battle with the resurrected Palpatine, Rey reaches out to the Jedi who have come before her. We hear many different Jedi over the years from various Star Wars shows and movies speaking to her and encouraging her to rise. This was cool and everything, but it would’ve been even better to see them as ghosts.
If it were shot the same way with her looking beyond the battle in the atmosphere and into space, there could’ve been faint Force ghost outlines of all the Jedi speaking. It would’ve been especially moving to see Anakin Skywalker. His story is the heart of the first six films, and not having him mentioned much at all in the Sequel Trilogy was a mistake.
Seeing him assist Rey at the end to help defeat his former master, and not just hearing his voice, would’ve been a nice cyclical wrap up to the nine-part saga.