I don't feel any need to argue about your interpretation of attack, obviously if you read it in as a hostile action, then a dragon's breath would be an attack. (I don't really understand why frightful presence would be ambiguous, nor why it depends on the dragon picking targets. It doesn't select targets when it breaths. What if it breathed fire in an area it thought was unoccupied, but actually there was a creature hiding there?)
But I would be happy to understand why you think interpreting it broadly is better than interpreting it narrowly. It is clear that you understand how the narrow interpretation works.
It goes back to how 5E is written. The devs have explained many times that the intent was to use more casual, relaxed terminology. They specifically tried to not write the book in gamer speak.
Imagine for a moment you had never played D&D. Someone asks you one of the following
- Would you consider a dragon trying to kill you by breathing fire at you an attack?
- Do you think someone is attacking you if they throw a live grenade in your general vicinity with the intent of blowing you up?
- You are confronted by some bullies. One of them throws sand in your eyes blinding you momentarily while the other punches you. Did both bullies attack or just the one that punched you?
I don't care what the book says unless it overrides common sense or the common definition of a word. Despite what you claim the book never says "it is only considered an attack if you roll an attack roll". Therefore I use the standard real-world dictionary definition of "attack". That does mean some DMs will rule differently in some cases.
It's not about which ruling is "better". It's about how the rules only apply when and if they override basic logic or common usage definitions of words.