I would be afraid players level up real fast and then they feel there’s nothing to accomplish anymore, so they leave the game. I find building times long, but at least they’re clear. You know how long upgrading a certain building will take, so you know what level your buildings will be next month.
What frustrates me is the ascension materials. You can wait for months for a certain one and still not have it. But worse, you don’t have a clue if it is going to drop for you in the months to come.