I believe that what helped me the most (I've been using vim for 4+ years now, but still not an expert by any means) is buying a keyboard without arrow keys and

I believe that what helped me the most (I've been using vim for 4+ years now, but still not an expert by any means) is buying a keyboard without arrow keys and also, getting used to vim motions. Vim motions are amazing. People don't use them. If they did, it doesn't matter what the plugins did, you can use motions with fancy stuff that plugins provide. Also your argument against not installing an autocompleter is without basis. Just because vim can do it natively does not mean its good. The native suggestions are alright when I'm editing on a remote server but I use YouCompleteMe when possible on my own systems. People who are used to intellisense etc kinda need this to do their job and still use vim.