There were lots of reasons for the Great Drought of 2008-2017 but I don't believe a fundamental coaching change in speed and ball-playing was the primary cause.
Thanks Ace
One of the catalysts for change was the adoption of pods and increased sizes by Scots College in 2009. They worked on the premise that size was the key and for a five years they were correct as schools had no idea on how to counter them. At times Newington matched them with their Pacific monsters, but Joeys were still using the Brother Anthony model which worked a treat when all sides were pretty much the same size. Scots were able to overcome the natural falling away in fitness for these HUGE lads by utilizing the most desired training facility in Sydney. When a school has equipment that professional rugby league has no access too, then you know that you are in an arms race. So for a few years the adage "might is right" held sway in the GPS.
How did Joeys respond?
The game plan since Brother Henry was to always meet them face to face and for a small time in a game, Joeys held their ground but the "bash it up and hope to offload" was not working as the larger teams were swallowing them up and sapping the Joeys boys energy. Joeys decided on a new game plan in 2018 at the early part of the season. It is no secret that the team held an "intervention" with one of the coaches. The system that Boyd had introduced was not working now as it had done in his era (the coach even played under Boyd). Something had to be done. The coaches listened and started to tinker with Boyd's plan. "How do we slay the monsters?"
FIRST they have a very strong front row, still mobile, but strong enough to win scrums. Use the scrum as a weapon and use it to launch the backs where the match ups is even. A new S&C coach was brought in, Kevin "Blood & Guts" O'Kane who worked wonders developing core strength and powerful legs. If anyone saw the Joeys/GPS front row (much smaller than the CAS) in 2021 decimate the CAS lads at Knox can attest to the skill and STRENGTH.
SECOND. Game play saw the Joeys forwards move beyond running the 10 and 12 channel. In fact at times second rowers passed the ball rather than hit it up. There was not just one linking forward (6) but everyone could now do this. The Joeys 10 was able to have more width and less traffic to deal with, plus a healthy use of dancing feet was employed by the 12 and 13. Joeys 12 in 2018 ran riot most of the season as he was now able to use the space in front of him. Defenses found it hard to set their big men into a defensive pattern when all of a sudden the ball was being shifted quickly away to the 13 channel and there was at times hard running props there hitting it from there. Opposition 12/13 were now having to tackle the Joeys front rowers which saw in the end, holes open up when the ball was shifted again.
The changes were subtle to the naked eye, but you can see the change in attitude as well. Suddenly there was belief again as they were now using a style that most schools had no match to. Kings played an excellent game in 2020 against a very tired Joeys team who had been beaten up and bruised by View the week before. Who knows who would have won if Joeys had an easier match before?
Anyway, Ace this was a longer response than intended but I hope I have added to the discussion.
