Does Mastodon have an Instagram-esque mode now?
None of this is something most people want to be anywhere near. While mainstream social media has many flaws, at least I am grateful for the fact that it bans, discourages or significantly dilutes this kind of content so that it isn't visible in most cases.
Most Mastodon users feel the same way we do, and block users and instances that promote toxic content. Join an instance with similarly minded people and you will never see people be shitty in those specific ways because they're blocked from engaging entirely.
My single-user instance, for example, which is entirely free of "toxic content", even with an extremely critical viewpoint, is blocked by an admin of a popular public instance of 17k users, none of whom can follow me (or can I follow), simply because I publicly disagreed with him about the virtue of instance censorship.
These things tend to naturally centralize, and that's always going to enable small groups to have an invisible, unearned, outsized influence over what people can see or read.
I think client-server is the wrong model for p2p networks. Look at the issues with the deliverability cartel and the relative inability of normal people to deliver messages to Gmail users without paying money into it.