If most teams get that right, that mostly means that most Rule 5 draftees just spend Spring Training with a different club (and in a major-league camp), then return to where they were. It only becomes a problem for a prospect's career if they're stashed on a major-league roster when they need AAA time to develop (kind of like Johan Rojas - which suggests that this isn't just a Rule 5 thing!). If the drafting club judges correctly, they either have a useful player, or they send him back - or in some cases, they work a deal with the player's former club, acquire rights to the player, and send him down (Victorino).
Moreover, we are, by and large, talking about relatively marginal prospects here. It's not at all clear to me that some of these guys (some of those who do get stashed, and "lose development time") aren't just as well off getting a year of major-league salary, and possibly some additional seasons, as opposed to being in the minors for that year. If they weren't drafted, some of them might never actually get to a 40-man roster. For instance, Castellano. If he had not been drafted this week, would he have been in the Phils' 2025 plans? Not obviously. Throw in a shoulder injury in AA, sometime this summer, and he might never, ever see a major-league paycheck. Stuff happens.
Jorge Bell was an anomaly, because the Phillies knew full well that he was a blue-chip prospect. They tried to play a stupid game - thinking everybody else would believe he was injured, working him out "in private" - and they got burned. That was not due to a flaw in the Rule 5 process; that was incompetence (which the Phils' organization at the time, lest we forget, was really good at!) That was up there with "throwing in" Ryne Sandberg in what was otherwise a straight-up swap of shortstops, to get rid of a guy who rubbed some folks the wrong way.
We should all remember where the Phillies organization has been...when we set out to complain about where they are now!