If Reagan was a candidate today

He would be excoriated by various factions of the party for his:

Signing some of the biggest tax increases in history.

Signing the Amnesty bill that helped create the current crisis.

Signing a bill that expanded abortion rights in Florida.

Nominating Sandra Day O'Connor to the bench in keeping with a campaign promise to appoint a woman to the court, a classic example of affirmative action.

The point is that the GOP has pretty much doomed itself to political purgatory by setting standards that even the standard bearer did not meet.

In short, even Reagan was no Reagan.

Signed a bill that expanded abortion rights in Cali.

Your points are well taken and incisive, ideology can be torn away from the person professing it, and the means by which they apply it (as in Reagan's shortcomings at the time and the political situations limiting the application of that ideology (i.e. a Democrat controlled congress)) But an insufficient application of the policy is not a negation of the ideal itself. It is still something to strive for, and at a time when we are adrift in factionalism even amongst our own party, it never hurts to look back on the ideals that defined and refined the reason we supported the party in the first place.