Rants are part of the analysis process ( normally with me it ends with "how did I miss that) so Rant on matey 😅 You are probably on the money with one of the New parts having a fault.
One of our sons friend had a problem that was down to the "O" ring seal on the fuel rail pressure sensor. The sensor was new and was fitted by a Garage that had carried out the work similar to yours, car started fine was driven home and sat on his drive for a coupe of days then wouldn't start ?? The Garage due to pressure of work couldn't help for a few days that's when our son volunteered me. We started at the tank and filter and we worked our way forward it was when checking the fuel rail pressure sensor we found a small crack/split in the "O" ring it was enough to not let rail pressure reach and hold sufficient pressure The Garage supplied him a new sensor (FOC) we fitted it and after around a dozen or so cranks it fired up and touch wood is still running OK. His Garage had never seen it before nor had I and personally wouldn't have suspected such a tiny split could be the cause.
Hope you find it soon
Dave