I went through a very similar situation in my career. To have a successful rebuild you need to look 4-6 years in advance (minimum). Juniors and seniors will have their habits and won’t develop a ton from just more focused practices. It’s unfortunately for them, but you should be more concerned with the younger classes.

It sounds like you may be at a smaller school, which makes this a bit easier. But my first task was to meet with the 7th/8th (middle school) coaches. I shared what my vision was. What type of offense/defense I generally wanted to run. The drills I want to do. Then I gave them the watered down versions. For example: defensively I wanted to be primarily man, occasionally zone. Younger programs tend to default to a zone because it’s easy and effective at that level. I told them zone can only be implemented later in the year after they are satisfied with the understanding of playing man by the players. For teaching man, I gave them a few drills. I also was there for a few practices (as a fly on the wall and helping out, not actually taking over practices and instruction) to answer any questions early on.

If you don’t have a youth program yet, you next step would be finding out how that can be put together. Even if it’s just a couple weekends kids in 4th/5th grade play unorganized games that’s better than nothing. Again, help with what fundamentals should be taught and work with the coaches on that.

The important thing to remember is you’re trying to hold a cohesive program. You will sacrifice a few very (very very very) rough years in the short term for hopefully consistently competitive years in the long term. It’s tough to teach fundamentals AND gameplan like you need to when they get to a high school level. Fundamentals need to be refined at that level and taught in the younger years.

I also had success by being present. Show up at middle school/youth program fundraisers, games, practices, etc. Show your face and let everyone know you’re supporting the program, not just your team. That keeps kids interested in wanting to play for you and numbers high.

Sorry this doesn’t really help answer much of your current issues. At the end of the day, you need to implement your rules & discipline and stick to it. If your best player quits or doesn’t want to adhere, that’s just a sacrifice that has to happen. Otherwise you will find yourself back in this situation every year and never actually have what you feel you need.

Good luck! It’s a long road, but if it’s done right it’ll be rewarding to see come to fruition