I disagree with your sweeping statements. Tradies fear crappy clients, but if you're pleasant to work with and you pay them fairly and you don't shit on them then you can find good tradies that will work closely with you.
Pick your tradie, to suit your requirements, and be a great PM and pay for quality work. I've been the Purchaser, Project Manager and often the apprentice/gofer too (saving myself many many billable hours of cost on each job).
The last three multi-thousand tradie jobs (builder, plumber, electrician) I've had deep interaction with the tradie and I am a repeated client with significant different jobs with each.
Properly respect the person, be ultra-polite if you want to question how anything is done. Never micro-manage or be an overdemanding perfectionist and accept normal mistakes. They are the experts but they sometimes get things wrong.
You are an apprentice trying to learn, but you can be firm with requirements and watch for gross mistakes.
I often get involved with other tradies or professionals too (recently car electrical, car mechanical, medical specialists, fencer). Sometimes to save money, sometimes to get job done better.
If you want to be OCD about a job, then pick an OCD tradie and be prepared to pay for your perfectionism. I'm usually more cowboy. One friend is a tiler, and he likes delivering amazing jobs (but he costs somewhat more per hour than average).
> and you just want them to install this OEM fuel pump which you've already purchased
Recently just done similar with my mechanic (supplied wheel studs and they've told me where to get replacement handbrake cable which they'll fit), and I did this with my electrician (used my own reels of cable) and I wish I did this with my plumber (because I would have made a better choice of fitting than they did). For cheaper jobs perhaps pay them for the lost income (trade discount or trade markups are usually known, or you can just ask). Actually did this with a fuel pump with the second hand car dealer when they had to fix under warrantee (helped simplify things to get their mechanic to fix car while I waited).
Context: I'm in New Zealand and I'm in my 50s.
On-topic: when you're a founder you need to hone the skill of working with professionals (e.g. lawyers) and getting them to do work right. My take on being a founder is that you are ignorant about everything but you have to get it done anyway: you often have to become your own expert and just do it (your meta-skills are most relevant). Advisors/mentors often lack context or have their own agendas, so you just gotta get ahead regardless of your ignorance. Learning how to listen to advice, pick the value out, and throw away the dross is just hard. Being submissive or falling for status plays is ruinous.