Like most things the true is probably somewhere in between and the effect is probably there, just not as strong as the original publication implied. Sprinkle a bit of placebo effect on top of that and that could lead to people (e.g. you) using the concept of ego depletion with a lot of success.
> The most famous and widespread case of a successful habit change is perhaps the 12-step Alcoholics Anonymous program
It's a reach to call it a "successful habit change" given that actual study show a success rate of less than 3%.
> We also know that we all have a limited supply of willpower.
Actually it looks like that isn't the case after all.
Etc.