Just about every 4X game you can think of is slow to get started. Sid Meier's Civilization, Stellaris, Space Empires... These games are long and slow to start, to the point that I'm pretty convinced the entire genre is this by definition.
The problem with games like these is that you need a lot of time on your hands to be able to commit to them, at least if you want to play multiplayer, especially with more than one other person, which IMO is the most interesting side of these types of games. Of course, in single-player, you can play at your own pace and be just fine throughout, which is also quite fun.