Guides are not for navigation
Also they are not only guides, but concierge, translators and "scam protectors"
Google maps can't show you interesting places (at least can't suggest) if places aren't on main "touristic roads", it can't tell you "avoid this crowded place", can't say on local language "I insist to use meter" in taxi, can't call to local theater and reserve seat, and for sure can't offer to spend 2-3 days in real local village home
With navigation you can easy find place if you know about him, but navigation can't help you when you don't know about that place exist, also navigation nor google map can't help you to plan visits.