I don't the problem was the maturity of the technology (much of it very quickly migrated over to Google Docs soon after the Wave shutdown). Wave was built in the original Google model of an open garden; parts of it were based on XMPP (like Talk was) and all of it was designed to support multi-instancing and federation between instances similar to both XMPP and email. It launched just in time for the Google+ efforts to decide the future of Google was only in an entirely proprietary walled garden.