This is an interesting question. I was thinking for a while about it and came to conclusion that I haven't heard many headphones outside of the mainstream hifi. The ones that I've heard were way more deliberate that I could ever make them, except for Grado. The Grados I heard years ago were like hearing aid. I guess people with hearing impairment can have their hifi too.

Most pointless products that I bought however must be some multi-driver Chi-fi earphones. Really badly executed products from TRN and KZ. I keep them stored in hope that some day I'll retune them.

I was also disappointed with Shure. Not bad, not terrible, just uninteresting. You can see how many popular products in hifi were iterated even 10 times before reaching high status. Sennheiser is an example. I used to have their HD545 which was to a degree a precursor to HD600. You can see a clear direction of development there. They not only know what they are doing. They persisted for a long time. Same applies to KEF in the speaker world. Refinement takes time.

Most small manufacturers either make planar drivers, or use freeedge dynamic drivers found in Denon, Fostex and Creative. They're available online. You can have fun with them too and have a no-bullshit set of cans :)I'm personally happy with modded Fostex T40RP. Nothing too fancy, but gets the work done.