This season has been extra bad because it released at the same time than Occult Crescent. The first week was absolutely dead in ranked. It's already problematic when it releases during savage releases, but savage at least generally leaves time for people to play in the evenings their groups don't raid. This time however, it's been a disaster. I actually wanted to take advantage that it happened on my DC to play more than when it is on the other one (which is also a huge detriment to play rates btw), and I couldn't even. Add to that that the high end crowd only starts queuing at crazy times like 22:00 or midnight and you end up with dead queues.
To reply to the OP: generally ranked is extremely FOMO and you'll need to be active in the first weeks of each season, that's when people play before it peters out. Sometimes there is a resurgence in the last week before the next season patch that you can try and take advantage of.