Except for Ted Cruz, perhaps, but your point is taken.
The problem with the GOP is not so much the slate of candidates, but rather the "base" and the machinery of the party. Stuck in a bit of an electoral tailspin (at least on the Presidential side), the path to nomination in most places can only occur by appealing to an increasingly shrinking base of the white populist right; under-educated, under-earning, and diminishing in importance and number but growing in anger. Since 2008, this group has shown it cannot carry a Presidential election.
I do believe that as a whole, America is a slightly center-right country politically. Which is what makes this so astounding - in recent times, such rhetoric would have been limited to fringe candidates in the impoverished south. Today, it is not only discussed loudly within the GOP base, but endorsed by a seeming plurality of registered Republicans. What a sad fall from Mitt Romney (which is a sad statement in its own right).
Much as Obama could not have existed without W. Bush, Trump could not have existed without Obama. Unlike Obama, he will certainly not be President and has no "purple" element to him, but with leave a crap-stain on the GOP not easily washed off. By the mid-2020s, the changing demographics of America will make all of this a very moot point (when Texas goes Blue, the party is over), but the GOP can either painfully swim against the currents of demographics or get washed into the sewer by that same river.