Do you follow someone, and you enjoy their posts but they boost too much stuff?
You can mute just their boosts if you want:
1. Open your Mastodon app or log in through your server’s website
2. Go to the profile of the person whose boosts you want to hide
3. Click on the ︙or ⋯ button at the top and select Hide Boosts From... (or Hide Reblogs on some apps)
4. If you change your mind, go back to their profile and select Show Boosts From… (or Show Reblogs)