I don't understand the problem. We posted about how easy it is - heck, as far as I am concerned, an embouchure change is not even necessary.
We need to identify the basics and then feed them to build a real foundation upon which the rest becomes much easier. We have no reason to blame Arban for improperly supervised activities.
If you get a solid daily routine, everything gets easier.
One thing that MANY get wrong: the Arban book is a CONSERVATORY METHOD and was not originally conceived for self help players. While it is possible to "NOT" have a teacher and it may even be better to have "NO" teacher instead of a "BAD" one, my take is that regardless of the discipline in focus: when we cannot judge the plausibility of what we do, the risks are higher. Self help trumpet means that we have a lot of bad options that we can take - and even get recommended by posters here with far more problems than you have.
I still use the Arban book. It is not my only book, but would be if I was only allowed to take ONE to a lonely island.
I certainly hope that this is not frustration due to the fact that the silver bullets are now viewed in their proper light.
I am 57 and we can teach old dogs new tricks - if they are willing to listen.