But I want to level up. And I'm not really motivated to play a game in practice.
Then level up. It's not that hard. Custom scenarios are in no way needed to level up, as there's a ton of ways to get points. Try playing some open games, get some achievements, join the ladders, play coin games (i heard those get you a lot if you win). There's always lotteries to play too. No need to play games with custom scenarios just for the points; probably just for the fun of the scenario.