But microwave was fine?

Trying to make dongle comparison with headphones is solid point.

Is the Bluetooth connection using headphones dac/amp and wired is not?

The important part of headphones doesn’t advance as fast as technology and construction elements. A dac will advance but a tube amp or well made drivers will probably still be great.

Next level wisdom

I think it’s a very subjective thing. Reference headphones are approaching perfect for some but also sound flat for others. Beats headphones are fun and perfect for some but are useless for others.

Maybe headphone companies are just chasing what segment of the market is currently spending the most money.

Buy a very cheap DD iem, and a very cheap BA iem to give yourself a frame of reference for driver style and fit. Then research and make an informed decision about one good pair that you’ll be comfortable with for a long time.