I want to know how I can make the kick and the bass make a perfect low end without complications and in a simple, practical and perfect way.
In my humble experience the pitch would be the first and most important aspect to address. Especially the pitch of the kick - no matter if it’s a live kick or a sample - the best way to fit with the bass is the pitch.
Then I would say the length/decay of the kick and bass.
Then I go by - balance - eq -dynamics
I totally agree with considerng pitch first. I just had an interesting situation the other day doing a mix critique for a friend. In the song he sent over there was very little to no info under ~50hz. I had suggested doing the Pultec trick to recover some of the low end that was missing and in this particular instance this was exactly what was needed: a sub boost and a dip in the 100-130hz region to clear out the mid. He initially dismissed my suggestion because the trick is so “basic” how could it be the solution? Same with your suggestion of pitch then ADSR. Occams Razor.