Who really says that though? As a regular lurker on the vim/neovim subreddits and mailing lists, I've never seen anyone try to fix someone's issue in vim by telling them to get neovim (literally never). Because, in the end, they're going to end up with the same issue. You already know what neovim is....so why would switching solve anything? Say they don't know how to use tabs, omnicompletion...why would neovim be any different?
Now what you may see, to your point, is people pushing (one of the many versions of) Spacevim on those forums. And they are shat upon rather immediately. It does happen though. But that at least makes sense, because those programs make using vim "easier", therefore eliminating issues users may have.
But neovim? Certainly not. The only time that would be a suggestion for someone is if they want some of the features neovim has over stock vim (maybe they want saner defaults, for example, or don't like tmux and want an integrated terminal).
As I said before I have no problem with neovim. Yet, I'm reading HN from about 3 years and I see more and more posts like quoted above. Even in this thread was one or two - dunno where they are now.
My point here is only to learn first and extend further. Not throw yourself into high water with SpaceVim and than say how much vim or neovim is bloated.
