The default subs are really toxic, for sure, but it seems like the 'shithole threshold' is a sufficiently large subscriber count. Especially when the subreddit gets the attention of the admins and powermods get pulled in.
Or even small subs that are against the prevailing opinions of the plurality of the userbase of all of reddit.
Those regularily get called out as "bad", "toxic" or "hateful". Or banned.
Which actually is the reason I got rid of my reddit accounts.
Every sub has its sacred cows that you can’t question. It just takes a while to figure them out sometimes.