It's not specific to the internet. It's just that basically everyone came into the internet when it became cheap and easy enough to use. However, previously it was only a subset of people who were willing to put in the effort because it offered some benefits to them.

It is simply the typical effect of regression to the mean of large groups. Previously there was the illusion of meshing because the group was more homogenous. Diversity is touted as a panacea, but it actually has many deleterious effects, the most obvious being the reduction of what is deemed acceptable/normal behavior and speech.

It is not surprising that everyone looks like an NPC because bringing everyone into the fold requires a redefinition of what is considered the acceptable norm. It systematically goes through narrowing the definition to artificially create the illusion of homogeneity (necessary to reduce conflicts).

This is the same process happening to society at large. Psychology is just a replacement for religion, and the various diagnostics just serve as a tool to police what is acceptable behavior. This is very much the same thing as the various religious scriptures, using moral arguments, appeals to emotions, and enforced tribalism to promote the “correct” way to live one's life.

The endless discussion of psychologists around diagnostics is hopeless; they are just gurus replacing preachers, but instead of using gospels and mythological stories, they use pseudoscientific bullshit to categorize/label behaviors and argue for what they believe should be the norm.