I get the argument and here's the counterpoint (to be clear I'm somewhat on the fence with this discussion, I see both sides so this is somewhat devils advocate):
How many guys on the team currently will be here next year? We actually don't know. We assume everyone not out of contract but guys could get traded etc. Even if we assume everyone minus Porter and Ennis (and random g League guys) return the expectations will be dramatically different next season because rookies will have had a full training camp and pre season to understand the system, Isaac will return, Fultz might return, we'll have at the very minimum 3 new players. With an off-season to work on their games some players might take leaps forward. We just don't know. Present doesn't necessarily predict future when you're dealing with guys 22 and under.
Also, nothing is stopping this team from playing good ball and going 12-5. The only thing stopping them is being talented enough and consistent enough to do that. Fans might complain and there'd be arguments about whether that's for the best long term but nobody in this organisation, presently at least, is deliberately stopping the young guys from going out there and winning games. In fact I'm sure Cliff is still very much setting up to win every game he can with the roster he's got at his disposal.