I finished all DiRT Showdown achievements in 2024.
For a game that can be bought for the literal equivalent of $1, I'd say it's a fun little arcadey spinoff of the dirt series that doesn't take itself too seriously and introduces some cool ideas and assets.
Like I don't understand why the acclaimed dirt 3 doesn't have the yokohama docks as a second gymkhana playground or the Mustang GT as a gymkhana car, but I digress.
The online multiplayer scene in the game is pretty much dead in 2024 so you will need to find a group to grind with to get those achievements.