Quotes from the video:

On what's lacking with native completions:

""But there there is one thing that is lacking and I will be honest. it is the fact that you can't like view the documentation. So I like viewing the documentation like when I'm looking at I want to know what health does I want to know what gsplit does. I want to be able to see it without having to go into the help document the help docs to view what that function does.""

and

"The current omnicomplete doesn't support adding more than one source. So, the LSP is one source of the completion. You can't add another source, which is then the snippet engine like LuaSnip"