[2020] Should I buy Cities: Skylines?

If you buy the game through Steam, you also have the option to get a refund. Just make sure you play no more than 2 hours and apply for the refund within a week of buying the game. That can serve as a way to test it out and see if you like it.

I would also start with just the basegame. It's on sale atm, so if you end up passing the 2 hours, but still abandon it, you won't have spent a lot of money on something you won't end up playing. DLCs can always be added later on to expand the game if you like it. And if the base game doesn't appeal to you, the DLC are unlikely to have made a difference. They improve the game, but the basics are the same. :)