The main turn-off people cite to me is our association with GNU. As a particularly poignant case study, in conversations with someone who has contributed significantly to Guix on my recommendation and did not stay around, the primary complaint was not the email-based workflow (which was noted as unusual but not overwhelming), but that the GNU affiliation *makes them feel uncomfortable in our community*.
Since this argument is based off personal anecdote, I want to add my voice to that; if guix split from GNU and the FSF I would become equally hesitant to continue using and contributing to it. Endorsement and ties to these projects comes with a guarantee of freedom, which is important beyond anything else. If we're all in it for the same purpose, why split over petty differences in personal opinions unrelated to those goals? You can't please everyone and proposing that guix cut ties with the two biggest players in the free software world would alienate more people - and more relevant people - than it would appease. This seems like a poorly evaluated proposal and standpoint that should be scrutinized and reconsidered.
