Apart from ET, if we don't sign KD, we don't have to lose anybody from last season's roster.
DA could simply resign the others, add Al Horford and call it an offseason. In this case, would there be any doubt Cs roster was better than last year's?I don't think so.
Given that, IF Danny doesn't bring the band together and decide to change pieces, he probably believes the team will be getting better by not doing so. Any FA that eventually replaces Zeller, Sully or JJ is suposed to be better in terms of production/contract, otherwise Danny wouldn't give up on them.