The "doom/dread" spoken of is not the doom/dread you are associating it with. Anxiety disorder (regular panic attacks) absolutely comes with a sudden feeling of impending doom/dread. That is its most characteristic trait!

Sufferers of panic disorder sometimes feel so convinced they are going to die imminently they end up in the emergency room, only to be told there is nothing physically wrong and that they are suffering a panic attack.

And generalised anxiety can result in a fairly consistent state of anxiety about things with a vague sense of impending doom.

I agree panic attacks are not a constant feeling of doom/dread. They have a sudden onset and usually pass within minutes (though can reoccur regularly for hours or longer when unmanaged). This can then be followed by a constant jitteriness, even shaking, feeling weak and feeling anxious for days or even weeks following a bad attack.

Also, anxiety attacks are not necessarily triggered by drugs/caffeine or a trigger situation. They can occur completely randomly when perfectly calm and relaxed and not thinking about anything in particular.

I also agree anxiety is very distinct from depression. But the two often occur together.