Additive subtraction

What do you see as the stricter, more absolute and critical points in the electron pathway, points where more attention to quality of material, geometry, mechanical aspects (the lot of it) is required in order to keep a good signal? Somehow, all things considered, it seems like every single thing is important.
When I learn more, a purist in my head nags more and more and I start fretting about the amount of “basic” solder and wimpy leads inside my gear, et cetera. I also realize to not fret about certain things which I previously considered bigger bottlenecks. A well-designed brass base metal binding post doesn’t seem so bad since there’s only a pair, but the little things that add up in hundreds worry me.
Certainly all terminals and corresponding cable terminations are strict points to consider, there can be significant loss if they are poor and significant less loss and leaps in fidelity can be had with better ones, it’s just that that’s subduing loss between planes of great additive loss in most cases. Even with good cables. We don’t usually see components’ internal cabling with any notable geometry or material, if we’re lucky the gauge can be sufficient and the dielectric not PVC… And it’s not Audio Note solder or even Cardas solder, it’s basic solder and that takes a great toll on the signal along the way.

Yesterday I took off the skinny leads going to my DAC’s transformer from a 4-pin connector, I took off the connector and soldered straight to the pins some hollow QED silver-plated speaker cable, that made a big difference, more than expected. Will do the same to the leads from the secondary when I get more solder, and will now have to keep doing similar things to all my gear… So much potential to be unlocked.