How would John Harrison (before writers changed him into Khan) have been another rip-off?
Before the writers changed him, it may not have been.
But that meme is a suggestion to people who say that it could have been one of Khan's followers. And all I wonder about that is why? Why not just use Khan? No one really gives a shit about Joachim or any of Khan's underlings. If you're gonna do a genetically engineered human, then make it Khan.
But if they didn't go with Khan, it's hard to say because the story would have likely been very different. A lot of the Khan-type stuff might not have been in there, although I'm sure there still would have been comparisons.
Take Khan out. Take genetic engineering out. Harrison is just a starfleet bad guy. Fandom would proceed to complain about the Insurrection ripoff.