>A fleeting sexual thought about a stranger who happens to be providing a service to you in that moment (hair brushing, apparently) has nothing to do with eroticism

I argue that's eroticism in its purest form.

>a quality that causes sexual feelings, as well as a philosophical contemplation concerning the aesthetics of sexual desire, sensuality, and romantic love.

both subjects don't need to be purposefully sexualizing for an erotic event to happen. That's a bit of what powers some of the more out there fetishes (like say, having your feet massaged, which has nerve connections to many more part of the body than one expects). It can escalate to something sexual, but most adult humans tend to learn how to suppress such desires, no different than not buying that candy at the store or hot wanting to slap Bob at work when he talks about the latest conspiracy theory.

>eroticism properly understood (i.e. turning actual consensual love, intimacy and perhaps even sexuality itself into a genuine, positive and human-affirming artform) is also quite dead

I guess so. The US has been so screwed on sexuality for decades that there's no one true meaning anymore. Which isn't bad, but when you range from "a person looked pretty" to "Onlyfans DM's" your word may indeed lose meaning.

It's interestingly enough a global issue too, in terms of policy. But unfortunately it's pretty low priority compared to the rest of everything else going on.

Eroticism is more about art and media. Being sexually aroused is not art, it is an occurrence in the real world.

This is like saying science fiction is talking to a chatbot. OP is being a bit pedantic.