Cordy was only the replacement in terms of what Angel needed --both the link to the PTB and as a confidante. That old Minear quote was amidst a portion of interview where he was talking about rewriting
Somnambulist for Wes instead of Doyle. One of the things he mentioned is that he gave Doyle's most significant scene (the rooftop at the end) to Cordelia. So, Cordy essentially became Doyle
for Angel not necessarily for anyone else.
For me, there was never anyone who could replace Doyle. He left a gaping hole that was never filled. Loved him so.
