While I understand the wish and need for ecumenism, its not so simple as saying, we should all just be Christians.
While the minor differences could simply be ignored in a collective church, what of the wider differences, the different beliefs held within the Church of the major issues like baby dedications/Christening, baptism, gifts of the spirit, Eucharist etc. These are not things that can be brushed under the carpet, some beliefs between difference denominations are outright incompatible, -someone- is wrong.
So yes, we must surly strive to maintain as unified as possible, but at the end of the day it is down to each believer to allow them to interpret scripture as God intended, and thus decide which denomination they personally reside in.