The answer is maturity. Structure does not hurt if it is chosen voluntarily. It feels good to do things exactly as intended.
Waking up at 6:30 doesn’t hurt if sleep started early and without being drunk.
The big tragedy is that society does everything to keep as many people as possible in a state of disarray. People to whom life is as described above don’t have the will to leave bad employment situations behind.
It’s one vote away. Every bigger city can have one school for early birds and one for night owls. Then parents can start work whenever they want. For that, companies can have flexible starting times. If they work in shifts, allow people to trade shifts so that some do all the early and some do all the late shifts.
Without artificial light, there were no sleep problems because more than enough hours were darkness. People took breaks from sleep.
https://en.m.wikipedia.org/wiki/Polyphasic_sleep