I have spent more evenings than I will admit chasing a level bed with a folded sheet of paper, turning four thumbwheels in a small ritual that never quite converges. You level the back left, the front right drifts. You fix that, the back left has moved. The bed is not flat. It was never flat. The glass has a gentle dip in the middle that you can feel with a fingernail, and no amount of corner-twiddling fixes a curve with four points.
The thing that ended the war was admitting the bed will always be slightly wrong and asking the firmware to compensate instead of fight it. I fitted a BLTouch, turned on mesh bed levelling, and let it probe a five by five grid before each print. Now the nozzle follows the actual surface, dip and all, lifting and dropping a fraction of a millimetre as it crosses the curve. The first layer goes down even from corner to centre, which it never did when I was the one doing the measuring.
The paper trick still has its place. You need one decent manual level to give the probe a sane starting offset, and the Z offset itself is still tuned by eye on a test square. But the per-print grind is gone. The machine measures, the machine adjusts, and I get my evenings back. Sometimes the answer to a hardware problem is to stop demanding the hardware be perfect and let some software hold the difference for you.