I know people are weird about stuff randomly appearing in their game library. If you are like the billions of people who remember back in the day when U2 decided to force everyone on the objectively terrible iTunes platform to include their presumably terrible album in their library without consent, then you are in very good company! Here are the instructions on how to get rid of this thing if you don't want it for whatever subjective reason.

Step 1: Click on your game library
Step 2: Find the "The Jackbox Megapicker" in your Steam library
Step 3: Right click on "The Jackbox Megapicker"
Step 4: Hover over "Manage >"
Step 5: Hover over "Remove from account"
Step 6: The follow popup dialog box thingie will appear saying:

Remove from your account
The Jackbox Megapicker was added to your account with a free license. You can remove it from your account so it is no longer included in your Steam Library and the list of games you own.

Would you like to remove The Jackbox Megapicker from your account?

Step 7: Click "Remove"

And with that you should be good to go!