To get a good feed on Mastodon, you have to set it up yourself. The best way to do this, as others have mentioned, is to choose a few hashtags of interest and follow them. This will show posts from accounts talking about those things, at which point you should start following accounts liberally (you can always unfollow later). Those accounts, in turn, will "boost" posts from people they follow, which is how you get exposed to the conversations happening there.

It's this process for populating your feed with content that's interesting to you that many people find intimidating. The down side is that you don't automatically get fed content like on Twitter; the up side is that you have a lot more control over what content you see.