Spot on thinking Martin.
I dunno if the caliper is a sliding pin type (I can't remember!) but suspect it is. From observation, this type rely on everything being right to achieve maximum efficiency of converting the effort applied to the lever into pressure applied to the disc surface. Worn disc, steps in the pins from wear, dry and dirty surfaces etc all rob precious force, wasting effort in overcoming friction and acting to distort the assembly instead of pressing the pads onto the disc. In tip top condition you can double the efficiency of a worn/dirty assembly. This is before we start think about old hoses, old fluid etc.
Nightmare city !!
The joys of owning bikes that have been around the block a few times. 😂😂😂
By turns frustrating and rewarding.