Have we as Aikidoka begun to accept a culture of martial mediocrity within our art?
No, I think we acknowledge it exists rather than passively accepting it, which does leave aikido open to heavy soul-searching on it's martial applicability, but on the plus side at least lets us re-evaluate things .
For me, there are several areas in aikido which lead to it's bashing as a martial art. Aikido has a very broad "church congregation" with a huge spectrum of reasons for training in the art, many of which are not directly connected to it's defensive value. The emphasis in some dojos on tradition, etiquette and a nicely turned out pleat in the hakama can lead to the "cult" tag being applied. Then there's the old bugaboo of cooperative training.
However, all these aside, I believe the main reason aikido comes under quite heavy criticism is that increasingly competition in a sport environment is seen as the true test of a technique, rightly or wrongly depending on your viewpoint. I think you'll find your own style of shodokan is increasingly viewed as the "best" form of aikido on many non-aikido sites for the very reason it used to be slated by more "traditional" styles.
As regards your point concerning losing the aikido in order to use brand x martial art, much more difficult to gage. While I think I know what you mean (and am guilty of it myself), as we can't get two dojos to normally agree on what is an isn't aikido I don't see how you'd address this. Where I think aikido should borrow and happily steal from any and all other arts is in the attacks, which, as has been alluded to before, I feel is the area of cross training that would benefit aikido the most.
Nice question, now bugger off and train.