I cannot agree. Rosario never coached the runners you are impressed with. They didn't go from Ben-coached to Alan-coached. They went from NCAA coaches to Culpepper. They are recent enough team additions that they weren't there pre-Culpepper.
The runners who actuall WERE around during the years Rosario led the team by himself performed very well, especially considering some were not blue chip recruits assumed to become world class. As a team, scored XC-style, they outperformed NOP, OTC-Elite, and Bowerman - combined - in both men's and women's OT marathons. Faubs, after quitting and donning Nikes, ran about 1 second per mile faster in Boston than he did in the original Carbon Rocket (not the Rocket X, in which Ali won the Trials) with a pure Rosario buildup.
What has happened recently is the addition of Culpepper, who had running chops (and successfully coached himself) in the 1500-10k. This was combined with recruiting runners whose primary events are in that range. Some of them WERE considered top recruits expectated to generate results we see recently.
Rosario's knowledge worked well in the half marathon and up range, and the old team was primarily runners best at those events. Their marathon schedules were very event-specific and similar to what a guy like Nate Jenkins (a huge Canova fan) or maybe Brad Hudson would prescribe. Steph chronicled a buildup on SM a while back listing the last 6 or 7 long runs and it showed an overdistance moderate run, a 16 mile MP run, and several workouts of the [2 mile@MP, 1mile moderate] type and similar sessions that totaled 22 or more miles with a good bit @ MP.
I do not fault what Ben did. He took runners who weren't necessarily teenage prodigies then multiple NCAA Champions to decent success including the Olympics. Now they have various mile and 5k type runners including top NCAA stars and a coach familiar with such events. The difference you see includes a new coach, true. It also includes blue chip recruits, more focus on shorter events, and a much larger team.