Bro Brosnan has never been a coach without at least one Young on the team. His first year coaching was Nico's freshman year. Nico's senior year was L&L's freshman year. He wasn't waiting until his 40s to show his brilliance, he showed it about 4 years after starting. I absolutely think Brosnan could do it at another school. He had decent results at UCLA while he was there for less than a year. Shame we didn't get to see if he could make NCAA champs out of it. Maybe if he can't get another coaching gig going, he will go back to HS and do it again. Who knows.
He talks in an interview (probably the HDrunners 2019 NXN video) about his progression with the team. When he started, he told his athletes that after 4 years, if they followed him, they'd win a state title. His first year, after not qualifying for League champs in 10+ years, they won it. His 2nd year, they missed the state meet, and he said it was his fault. He made mistakes and he learned a lot from them. The next year, they won the state meet. The year after, they won nationals.
I think the fact that they didn't even make the state meet in his 2nd year, he acknowledged his failures there, took responsibility for it, and then the next year they came back and won state, points to him being a good coach. A good coach isn't someone who makes no mistakes, it's someone learns from their mistakes. I pointed out that Soles had an immediate (and faster) impact at Herriman exactly for that reason. Soles was coming in with far more experience than Brosnan. Brosnan had to make some mistakes at first, just like literally anyone ever. What's the Edison quote? "I didn't fail at making a lightbulb 1000 times, I just found 1000 ways to not make a lightbulb before I figured out how to make 1" or something to that effect?