Be critical all you like, it's the way everyone on here learns. I agree, that true measurements are always better, but they take time that I don't feel is necessary. Call it experience I guess, but I feel I have a pretty good idea of what a good first layer looks like and have figured out the "feel" of my machine. If my extrusion width is right, it's pretty easy to tell when it is too low or two high. I have had extremely good luck with glue stick (get virtual zero lifting on everything but parts with sharp corners) without any "elephant foot" over extrusion.
Also, you are correct about glue thickness variation and that I why I always re-zero'd after re-application. This is also why I worked really hard to figure out the best way to get as many prints as possible out of each application. I wasn't unhappy with glue stick, just wanted to try the "magic
PEI build surface" that I keep reading about

.