The rebuild should be to get better scouts at all levels and improve instruction and medical. Also, we need to stop losing draft picks and international $ to FA signings. Better to re-sign Realmuto and avoid comped FAs,, if there even is still such a thing this winter. Also, don't trade minor league and young players away. We badly need cheap, team-controlled plus contributors to keep the budget controllable. An over cap season seems inevitable next year.
I would list our major deficiencies in this order, starting from most serious:
1. International scouting -- when we land a big $ prospect they are lacking talent or not the age stated. We are almost unique among teams who make a $ effort internationally, in the lack of plus MLB players. It is many years of failure and the finger must be pointed at Sal.
Instruction -- the players we sign don't seem to progress satisfactorily in the minors
The analytics department. It still doesn't seem to be a plus.
Pro scouting. We trade for and sign too many duds, including injured duds
draft scouting -- First round has improved greatly of late, because we have gone largely college. When we don't dare go H.S. position player, because we seem unable to pick the good ones. Perhaps it is the same failing which hinders us with even younger international position players.. We seem to have made a concerted effort in drafts and in signing undrafted this year in adding college pitchers who can be MLB relievers. We have come up fairly empty in that effort, whether scouting, development, or giving up to early.
Refusal or inability to be a factor in the international post-amateur player market
Logic says that if we have good baseball people in place, spending the amount of $ we are willing to spend should yield a far more positive result. I know little about the specific baseball people down the line, but our failure to produce young contributors suggests we have major weaknesses there.
The Phillies still seem too much a member of the Commissioner's Cub Scout troop, acting 'for the good of baseball', not pushing the boundaries by using the loopholes deliberately inserted into rules, and just having a flat-out determination to doing what is necessary (within the stretched limits of the rules). The scofflaws seem to do far better than us . Like Giles, MacPhail seems to have gotten his job for this reason.
I don't know if we rebuild or not, but suggest that if there is a high likelihood that we don't re-sign Realmuto and if there likely won't be fans in the seats to start next season (I think a real possibility), then next season would be an excellent time to rebuild. Otherwise, fans will revolt and the stadium will be a booers paradise. I am pessimistic that we re-sign Realmuto. I think more often than not "I won't negotiate until the season is over' is a tactic not to get on the bad side of fans and media, by a player who has already decided to skip town. I just don't think the quality of the MLB Phillies is such that Realmuto wants to cast his lot with us, especially since the next couple years don't look any more promising. The Phillies needed for their young position players to break out, and they haven't. If they can't turn around Kingery and Hoskins, the team is cooked for this cycle.
It would also be nice if they could build an actual bullpen.