This is probably futile and I shouldn't bother but I guess I do.
You said in your post about Efron's career today "He has had chances headlining movies and has failed every single time." - that's just simply not true.
I'm not going to get into his talent because that's a lot based on opinion but if you look at his movies with wide releases (what you call mainstream), he had at least 2 movies which qualify as successes post HSM.
The "golden rule" is an actor opening his movie above $20m is a star and a success (obviously not blockbusters or movies which sell themselves; I'm talking about small or medium sized movies which are sold on the actor).
And Efron has done that with 17 Again (which opened to $23.7 and made $135m ww on a $20m budget) and with The Lucky One (which opened to $22.5 and made $100m ww on a $25m budget). In both movies he was bascially the only draw and main selling point. They are not huge hits but they are moderate hits and definitely not failures.
He had 2 underperformers as lead since HSM, Charlie St. Cloud and That Awkward Moment. But 50% ain't that bad. And his upcoming Neighbors is going to be a success by every indication - critically and commercially.
Indies are obviously different and while they haven't turned out to be successes at the box office, he was still headlining movies which got into Cannes competition and Venice competition (twice). And those are the most prestigious film festivals around. Those are not some random ass indies nobody has heard of but he was working with high profile directors and cast.
Despite not being in a franchise or making many mainstream movies in the last few years, he was still on Vulture's 100 most valuable movie stars list this October (and that took his addiction problems already into account). That's a list which takes a lot of actual research data into consideration and he was actually on that list unlike many of your declared A-list stars.
Anyway, I probably wasted my energy here and this isn't going to change your mind - or Efron's career. And yes, he has a lot of challenges ahead and his addiction will surely cause some problems but his career so far is not the failure you make him out to be.