Then we have the new characters introduced in 2 and 3. Did most audiences really care about Holdo, Rose, the literally unnamed DJ, Jannah, or Zorri? Snoke had potential but that was cut off before anything could grow.
The difference is in TLJ the secondary characters move the character arcs along, whereas in TRoS they’re just kinda there.
In the end, there was no real arc for Finn, so that renders most of TLJ’s characters kinda there. Canto Bight, DJ, Rose…if Finn HAD died in TLJ, it would’ve been at least some form of resolution. The fakeout is basically the end of his character path in the sequels and it’s pretty weak.
Finn had a clear arc in The Last Jedi, and the clever thing was it was inverted from Rose’s even though the same experiences teach them the lessons. Rose and Poe’s arcs are to go from an “at all costs” approach, ready to sacrifice everything, to understanding that sometimes doing whatever it takes isn’t the same thing as doing it at all costs. Finn’s arc goes from a man without a cause, driven by fear, to becoming someone that understands there are things worth fighting for, even being ready to sacrifice himself. A lot of people say his arc is ruined since he doesn’t sacrifice himself, but that’s not true since he was actually ready to sacrifice himself. He was still making that choice.
While that’s true the arc could be seen that way, the fact that it had very little impact on the overall narrative renders Finn…boring. If that idea of him leading a Stormtrooper rebellion had come to fruition, that would’ve made his character’s progress throughout all 3 films something to follow on rewatches. As it stands, though, his impact overall is very minimal, despite being hyped as a major character with TFA. The general population don’t remember Finn (or even Poe), they basically remember Rey and Kylo. Even Boyega commented on how badly his character lost relevance as the trilogy progressed. Remember when he grabbed Luke’s saber and the sheer power it radiated as it ignited with his intense face? That scene in every trailer? The guy wanted to kill Kylo right then and there and there was an intensity to the fight. Then he slowly became a joke in TLJ and then full on comedic sidekick in ROS. Couple years and no one’s gonna remember him riding whatever CGI animal in either film.
That being said, it wouldn’t surprise me if the rumors are true and Boyega recants and comes back to Disney as Jedi Finn, especially now that Iger has admitted they screwed up and they need to draw back some disenfranchised fans. That footage will likely be usable with editing.