So if every reaction, action, motivation...

So if every reaction, action, motivation, anything we do in our lives can be boiled down to just brain chemicals then what are things like thoughts and ideas, judgement and analysis, love and attachment?

Particular patterns of brain chemicals.

Why do we place importance in them then? If that's brain chemicals too then how did humanity get here and what should anybody's purpose to live be?

>live to be

ftfy

>raison d'ĂȘtre

spooky

...

read literally the first lecture of varieties of religious experience

You're starting from a false premise. Neurotransmitters are important but they are not your thoughts or emotions. It's the network of neurons themselves which form your thoughts, memories, etc.

Chemical soup theory is old news, it posits that the oil runs the car with complete disregard for the engine.

Spoiler: material rationalism is wrong.

This is an argument about your feelings, and not the nature of reality. Ultimately you have to come to terms with it in your way