Honestly I wondered if John Barrowman was making a dig at Steven Moffat because of not being back on DW since he's been in charge, he obviously enjoyed playing the character and seemed annoyed in the past about not being invited back for the 50th anniversary celebrations, maybe he's decided that Steven Moffat has something against the character? But it seems bizarre to imply that Moffat would have any reason to block Torchwood as a show

It probably is mostly just a case of RTD being too busy, and I suppose that the BBC don't want to commission any more TW without him