Thats obviously not a primary concern. Similar to how your home kitchen isn't going to have a food inspector show up and close it.
My home kitchen doesn't routinely serve strangers. The forum I host trough a server in my cupboard does.
If you want to make a comparison, it's between a small family restaurant and a giant fast food chain. It may surprise you but food inspectors treat both in roughly the same way.
Face it. Nothing meaningfully separates my forum from giant social media companies apart from scale.
Hence, small forums hosted by hobbyists and volunteers should be shut down.
Most states have cottage food laws, with basic regulations for small-scale commercial production. E.g. you need to take a course on food safety, you need your water tested, and you can only sell up to $X per year, but you aren't subject to random inspections. There is no reason why the web shouldn't be regulated similarly, with different rules based on the size of the audience.
If we have different rules depending on scale, how is it OK for the rules for large scale social media platforms to be impossible to comply with by large scale social media platforms?
In practice though, it's not unreasonable to say that we should expect more from companies that can cause harms at a much larger scale. Perhaps there's some kind of threshold where we can accept some harm being done at a small scale while still not allowing harm at a much larger scale. Seems fair enough.