Unfortunately, in practice, Agile almost always devolves into a cargo cult: perform the ritual of the Standup at the appointed time, etc. and all will be well. Any actual personality management is papered over with appeals to authority.

I think teams that succeed do so despite using Agile (or any other management fad). A cohesive team that communicates well can succeed using Agile, sure, but the process is incidental; they would succeed using most any methodology. Survivorship bias leads people to believe that Agile (or whatever methodology-of-the-week is in play) is causative, when it is actually epiphenomenal.