The heat shield failure was a test and the result was a working heat shield, when it counted. That's the point of tests. NASA already had several working heat shields from the old missions but the new one needed testing - for the shape of the craft etc. They already had a lot of data from the old efforts (that worked).
I think that exit and re-entry are almost routine now, provided your rocket doesn't explode. The tricky bit is out there in space and trying to make the moon a resource of some sort.
