NeoVim devs earned that 'Neo' by rapidly adding features that were in demand for years (and were subsequently implemented in Vim, in response to NeoVim's new pace of innovation.
Anyway, adding Neo was enough to differentiate the two names, so what's the problem? Let's not forget that Vim did the same thing to Vi when it was named "Vi IMproved."
It's not the name in the neovim case, it's the tagline "literally the future of vim" when vim was still being actively developed by a different group. It is IMO immoral for me to start a site called "Hacker News 2.0: The successor to Hacker News" and start telling people that I'm the next version of it and that's how that comes off to me.
I understand your point, it does seem quite... rude? It reminds me of google calling their programming language "Go" while there was an existing language with that name already.
They didn't call it Vim 9, though. It would be more like if you had a forum called NeoHacker News. Similar to "Hacker News"? Yes. More alliterative? Also yes. Misleading? Potentially not, with the right communication.
Neovim was a fork of Vim so it makes sense to keep the name similar, this project seems to be a completely new codebase.