It's certainly possible that sayings of other people were later attributed to him, but to really make this case you'd need to have quotations that were attributed to multiple sources, including him, if you see what I mean. Absent that, it could be true, but there's no particular reason to believe it.
There are enough specific biographical details about Jesus of Nazareth to make it likely that there's a specific, real central figure. For example, the fact that he was from Nazareth was a problem for his early followers (it didn't match the Messianic prophecies), which is why they invented the odd story of the census, so that they could claim he'd been born in Bethlehem, the hometown of King David, from whom Jesus was supposedly descended. That seems unlikely to have happened if there hadn't been a real, central historical figure.
Also, none of the early non-Christian sources claim he wasn't real or that he was a composite, which they surely would have done if there was any doubt on the matter.
I agree with you that Jesus wasn't God, who doesn't exist, and that there were no miracles, which are impossible. However, this is not the same thing as saying that there's no evidence for the existence of Jesus, the Jewish apocalyptic preacher.
The earliest documents about Jesus, such as the Pauline Epistles, were written by people who knew people who knew him. In a mostly illiterate society 2,000 years ago, this is about as good as evidence gets. It's also the exact same kind of evidence as a journalist or researcher writing an account based on interviews with people. This was how, e.g, Herodotus wrote his histories. When Herodotus says 'A guy rode a dolphin once' we dismiss that. But we don't say 'The people in the Histories didn't exist, except those for whom there's physical evidence, which is about three of them, not including the author'. We do much the same with Jesus and the miracles.
If the Apostles had wanted, for some reason, to make up a guy, that would have been risky. Other people would have just said, 'That guy didn't exist'. If they had anyway decided to make up a guy, they'd have invented someone who actually fulfilled the Jewish propehcies of the Messiah, instead of inventing Jesus, who obviously didn't. This suggests they didn't invent him, which strengthens the plausibility of the evidence we do have.
A third way of looking at this is to ask if there are any comparable figures, religious founders from the historic era, who we now think were wholly made up in the way you're suggesting. But there aren't. The Buddha, Confucius, Mohammed, Zoroaster - they all certainly existed. Indeed, I can't think of any figures form the time period who were actually imaginary.
People are so convinced that if we're more cruel to criminals, they'll stop committing crimes, or if we're harsher to workers, we'll work harder, or if you're tough on border controls, immigrants will go away. It does not work and it cannot work.
In the original cut they did use the Latin alphabet, so this is, incredibly, yet another thing George Lucas did to make the first film retroactively annoying.
I kinda think that if you can imagine a one-line fix to a plot hole, it isn't really a plot hole.
I remember someone insisting to me that there was this huge plot hole in the film of the Fellowship of the Ring, because Merry and Pippin don't get told about what Frodo and Sam are actually doing until the Council of Elrond, but still willingly run around risking life and limb to help them. Now, not only is this not a plot hole in itself (I'm pretty sure I'd help anyone fleeing a demonic horseman, just on principle, never mind if that person was my lifelong friend/cousin), it's also quite obvious that they could have been told everything offscreen. The audience didn't need to hear all that explanation again, five minutes after we first heard it.
A lot of plot holes people like to complain about are basically of this nature. 'Can you imagine a fix?' Yep, easily. 'Did the audience need to hear it?' Nope, because I could easily imagine it. 'Well, there you go, then.'
