Who is The Last Jedi?

Is it Luke, Rey, Finn, or perhaps Osoka Tono?
I think it is probably Luke. I do not think Rey or Finn become Jedi. To understand why, we must ask why Luke is on Auck-To. Conventional foolishness suggests that he is there just moping around, depressed that Kylo destroyed his new generation of Jedi. However I think this is problematic; First, it would be very out of character for Luke to just mope around wile the galaxy goes to the dark side, and if he just wanted some hermetic place to mope around, there must have been at least a few billion such places in the galaxy that did not have a map leading to them.
Luke is at the first Jedi temple because he is looking for something…looking? Or perhaps found something he has hum?
There is a set photo from Pinewood studios, where TLJ is being filmed; showing an enormous set of an island similar to the one Rey finds Luke on the end of TFA. However, instead of steps leading up to a Jedi temple, they lead up to a large dead, or perhaps dormant, Tree. It is hard to imagine building such an enormous set for an inconsequential scene. The tree must be important. Could it be the very embodiment of the living Force itself? Dormant for eons since the Force first went out of balance? Is Rey there to heal it with the cyber crystal shard she found in the basement of an old woman with peculiar eye sight? Well, that might be a bit blatantly plagiaristic even for Star Wars, but I think we may be on the right track.
The original trilogy was a morality story about a farm boy who seeks connect with his dead father, finds out he is actually alive but evil, and strives to bring him back to good side. As such, Return of the Jedi was a good end to the story; with everything on a trajectory for happily ever after with Luke reconstituting the Jedi order.
The prequels, however, did not introduce Anakin as an unusually strong, idealist, crusading Jedi, who happened to fall to the dark side; but rather a long prophesied Chosen One, messiah figure destine to bring balance to the Force. At first this just seemed like narrative larceny - using unearned mythological language to make one of the characters seem more important than he is - as Anakin does not follow and discernable Chosen One arc (he is really just an above average Jedi, who happens to be at the right place at the right time), and no one seems to have any real notion of how exactly he is supposed to bring balance to the Force. Obi Wan does suggest that the chosen One was to "destroy the Sith", but if that is the case, someone really should have told Mace Windo, who, when going to confront a suspected Sith lord specifically did not take Anakin with him (I know, would that that were the worst problem with the prequels). Anakin did, of course, eventually destroy the Sith when he gave Sheave the shaft at the of ROTJ, but did that bring balance? It is difficult to see how this could be the case as all he really did with this was restore the status quo from the beginning of Ep.I, with the Jedi in the midst of an apparent millennial hegemony with the Sith thought to be extinct. Yet it was in this state that the Jedi were looking foreword to the coming Chosen One bringing balance. Also messiah figures don’t generally come to make minor repairs or cleanout one little problem. They typically come to bring a complete metamorphosis, a total transformation, tearing down the whole house to build a new one in its place.
So if we are to take the "balance" story arc seriously ROTJ can no longer be an adequate end, enter the ST. The first dialog of TFA (after a three movie hiatus) connects back to the balance arc with words  "without the Jedi there can be no balance" - words that will likely turnout to be ironic - so now the saga is one big balance mythos. Now the gold standard for the balance mythos in film, as I alluded to earlier, is The Dark Crystal (although if you prefer a 40 minuet version of the mythos, check out Star Trek: The Enemy Within). In the Dark Crystal the Skeksis are unquestionably the bad guys and the Mystics are the good ones. However, the mystics do not seek to overthrow the Skeksis and rule in Mystic hegemony, but rather the Mystics realize that both they themselves as well as the Skeksis must cease to be in order for the truly balanced being to return and insure in a new golden age. The prophesied catalyst for this were the gelflings, a male and female (gender balance is a common motif in the balance mythos). The male gelfling, though razed by the mystics was distinct from them as they realized that his destiny lay along a different path from theirs. The female gelfling knew nothing of the mystics and was raised by adoptive parents in another part of the world (sound familiar?) So in this analogy Anakin would initially be the catalyst destined to not only bring about end of the Sith but the Jedi as well, in order to make way for a new balanced order to bring a new golden age to the galaxy. So what happened? Well, the Mystic analogs in this case, the Jedi, like typical established elites of the currant system, failed to grasp the true purpose of the catalyst/messiah figure (a prophecy that misread could have been?) and instead ended up trying to co-opt and even undermine him by training him to be a Jedi against the counsel of their oldest and wisest member. Why did they think he was meant to be a Jedi? At least partly because Qui Gon thought "finding him was the will of the Force". But wait, Qui Gon did not find Anakin, Padme did. So perhaps the Force thought it was more important for Anakin to get involved with Padme than the Jedi? What were the fruits of Anakins involvement with Padme? As I recall it was twin children, a male and female, and the fruits Anakins involvement with the Jedi? A few decades of galactic tyranny and bloodshed...hum. It actually seems that the person who may have come the closest to putting Anakin on the right track was actually chancellor Pallpatien, when he told him to "embrace a larger view of the Force". It seems rather ironic that though Yoda harped on the dark siders for "spreading lies, deceit" and "creating mistrust", it actually the Jedi who seemed to need interesting "points of view" to justify their words, while the Sith lords seem to be the ones who just tell it like it is.
Moving on to the OT, the Mystic analogs are down to just Obi Wan and Yoda, with Luke and Leia as the catalyst. So how did they make the same mistake again? It is noteworthy that Obi Wan just told Luke to "learn about the Force" becoming a Jedi was actually Luke's idea, and Obi Wan's expression when he announced it was anything but ecstatic. Still, they did train Luke as a Jedi, caped by Yoda's now enigmatic last words "when gone am I, the last of the Jedi will you be". In any case they apparently did not have access to whatever Luke has found on Auch-To. Which brings us to the ST. Luke is now the lone Mystic analog with Rey the winged gelfling (but don’t worry, I am sure she has a male counterpart) and now Luke has the whole picture of what must be done to bring the balance, but not by a Jedi. Rey and her cousin will be the catalyst, to finish what their grandfather started.