What is technically considered an attack?

[smcmike]

It's battery, so yes.

Battery requires contact. This is why involving a whole second, and much larger, body of rules is probably a bad idea. If you think RAW is confusing or obtuse, boy, wait til you check out the common law.

Since RAW doesn't specify everything in a binary fashion that X is an Attack while Y is not an Attack, we only have RAI to go on.

This isn't true. RAW gives us a test. I don't know why you have discarded it.

The first question to ask before answering is: in what context are you asking what an attack is?

Because the answer, depending on context ranges from "actions resolved with a d20 attack roll" to "any action that can be read as hostile or otherwise putting a character in disadvantageous position"

The context is "any rule that refers to an attack."

You'd also need to go through every action to determine whether it's one attack or several. Whirlwind attack, magic missile, eldritch blast, etc. And nobody would agree.

Yup. Also, this adds in the concept of attacks that do not target a creature or object, so you have to deal with that.