Meta's has been listening to some concerns after all especially now after some pressure.
These changes very well could help parents moderate their teens. Meta's head of product says these changes address particular 3 concerns in an Npr interview.
Will this be the end of the complaints and concerns geared towards Instagram, probably not.
The normie services are increasingly tied to real world identities, through verification methods that involve phone numbers and often government-issued IDs. As the regulatory requirements tighten on these services, it'll be increasingly more difficult to create anonymous/alt accounts. Just because it was easy to anonymously create a new Gmail or a new Instagram account 10 years ago doesn't mean it's easy today. It's a common complaint that things like an Oculus requires a Meta account that requires some tedious verification.
I don't think it'll ever be perfect, but it will probably be enough for the network effects of these types of services to be severely dampened (and then a feedback loop where the difficult-to-use-as-a-teen services have too much friction and aren't being used, so nobody else feels it is worth the effort to set up). Especially if teens' parent-supervised accounts are locked to their devices, in an increasingly cloud-reliant hardware world.