The question is, what would you have preferred? Because simply removing the astral projection from the scene, having it be a simple action scene played absolutely straight, not only would it create a ton of problems, but it’s the exact kind of thing I’d expect from a hypothetical version of the sequel trilogy that was actually nothing but a lazy cash grab, no creative energy involved.
With all the rest of TLJ remaining the same, and the leadup to Luke’s appearance being the same, here’s what I would have done.
Imagine Luke did come there in person. Kylo insists on killing him personally, and orders that the First Order broadcast the fight on the Holonet, so that the whole galaxy can witness the death of Luke Skywalker. Maybe we even have shots of crowds watching holograms of the battle: on Coruscant, on Canto Bight (broom boy would be watching), on Naboo, etc. Kylo wants the whole galaxy to see as its last hope is snuffed out. Luke earnestly tries to talk him down and convince him to turn away from this path, and apologizes profusely for his actions towards Ben. It would be made clear that Luke still cares about him and sees the good in him. Kylo furiously lashes out, despite Luke’s best efforts, and the two have a physical duel. Show how much stronger Kylo has become since he is much less conflicted than before. His anger and hatred have become focused, and he is finally a force to be reckoned with on par with Vader. Luke puts up a valiant fight, but Kylo overpowers him, and wounds him severely, then again, and again.
All the while, the Resistance are making their escape, with Rey frantically trying to throw the rocks from the cave entrance one by one. The process of lifting each rock would be visibly taxing for her, and there would be a sense of a race against time as it could cut back and forth between her struggle to open the way and Luke’s battle with Kylo. Every time it seems that Luke is about to fall over in defeat, he gathers himself back up and stands defiantly, determined to buy the Resistance as much time as possible, and Kylo is getting angrier and more unhinged. Show how the Holonet broadcast is starting to have the opposite of its intended effect on the people of the galaxy. People are rallying behind Luke. They’re cheering him on and loudly encouraging him to keep fighting. Then, when Kylo finally strikes Luke down, and Kylo angrily flaunts his triumph over the martyred last Jedi, the galaxy watches in stunned silence and grief (maybe have Qui-Gon’s funeral theme playing). And that grief begins to stir inside of people, until it erupts in galaxy-wide revolution by Episode IX.
That would’ve messed me up emotionally. Maybe some people would consider this ending to be played too straight, but Star Wars is a melodrama at its core. It’s a simple story, but compelling in its simplicity and earnestness.