yes and no:
I'll start by stating that i am almost a complete novice when it comes to Auto electrical wiring. I mean i can do a neat job of things and I have a kit containing all the correct crimp terminals and crimpers but my experience really only goes as far as a basic understanding of how to wire things in a neat and functional way.
I haven't used an aftermarket kit such as painless or EZ.
However, i have wound up owning cars where the OEM wiring was butchered beyond belief. These cars haunted me with problems that only emerged at the most inopportune times leaving me late or stranded. *
At first i was really intimidated to do anything elec related. But as you educate yourself about auto elecs you find its not THAT hard to do yourself.
In each of these cars I sourced wiring looms from similar models and transplanted good for bad. There are tips and tricks to doing so such as labelling everything consistently and clearly, being careful marking and removing plugs and exercising caution around things like ecu pin outs in newer cars.
But since we are on a forum dedicated to Japenese Nostalgic cars one will assume that the car in question is probably something old and obscure.
I realise that you might not have access to a replacement loom. My advice would be to identify and remove any non-original wiring. Then repair what you have. If there are chopped up sections just re-join them (with the same colour wires - source from a wreck) or replace sections of wiring one by one. Use heat-shrink and tape as necessary.
The effort required to fix what you have versus a total re-wire is a no-brainer.
I would only resort to a aftermarket wiring kit as a LAST resort if i couldn't find a suitable replacement loom.
*In one recent case: 1985 Ford, Alternator died, battery voltage dropped, ecu went nuts, threw a stray spark, backfired on LPG (propane), destroyed airflow meter, insulation caught fire, melted wiring etc etc. I stood there and yelled at the car to encourage it to burn to the ground! But my buddy doused the flames with a bottle of coke. Was a half-day fix to get running again. Replaced at least 50% of the wiring in the engine bay.