Not sure how active this community is but this is such a frustrating oversight with the Android app that it's worth a shot.
I live in an area that is spotty for network. Whenever I'm in the car Spotify tries for ages (up to a minute) to load stuff over the network before l am able to interact with local playlists - not ideal when driving or waiting to set out.
For a music player I think it makes much so more sense to prioritise the loading of content and functions that are available when offline FIRST. i.e: downloaded playlists etc. BEFORE polling the servers for whatever recommendations or trying to load dynamic content that isn't already on the device etc.
It may be as simple as shortening the timeout for whatever it is that holds up loading local content but there is definitely a long lag of up to 60 seconds on opening the app which just isn't necessary when there's plenty of local music to crack on with.
I had thought that offline mode was the answer but it's still a case of setting the app to offline mode in advance which is no different to opening the app well before a car journey and doesn't really solve this wasteful network useage. Trying to put it in offline mode when in poor signal still results in the same long wait time.