People really vary in how their brains are wired. Different ratios of neurotransmitters, and receptors. So they tend to respond differently to drugs.

This has been a huge problem with antidepressants, which now we hear
"really don't even work" !

So what works for one person many be very different for another.
And some doctors do not like anyone questioning them, or making suggestions. I personally think those types of doctors are insecure, and become combative when threatened by knowledgeable patients.

I never took gabapentin. Luckily for me it wasn't available when I was at my PN worst, and today, I am loathe to even consider it. In fact only Elavil was around then! I tend to bloat/edema and I don't even want to try either gabapentin or Lyrica.