I have the same problem, although it eventually shows up. I've been complaining about this for years and the only response I get is to reinstall the app. Trust me, Spotify does not care about fixing any of the issues.
That is the impression I get also, I posted the same question a year ago, but that post has been removed it seems... I am currently in direct contact with them over Twitter though, so hopefully whoever is on the other end has a solution.
I have the same problem on my iMac (Late 2013, Mojave Version 10.14.3) but not on my iPhone or iPad. When opening Spotify the window is black for quiet a time. After some time I see on the left side the Start/Browse/Radio-button and my playlists. When choosing a playlist, on the right side is a spinning symbol. But I takes minutes until the songs of the playlist are visible. At least I can play the songs. Maybe it's my iMac which sometimes is very slow. But its is really annoying.
I am having the same problems. I just tried to do a clean reinstall and it's still coming up blank. It loads after maybe 10 minutes but you can't click anything or else it just freezes. This is insanely frustrating.
I'm running (or attempting to anyway) version 188.8.131.52.gb388fe17