I think you need something like restic with a retention policy

https://restic.readthedocs.io/en/stable/060_forget.html#removing-snapshots-according-to-a-policy

--keep-{hourly,daily,weekly,monthly,yearly}

other solutions that implement similar policies are kopia and rustic

the advantage of using an off the shelf solution is that it's almost certainly more reliable than what anyone can come up with in a few hours, and, it works with incremental backups, so your space requirements are drastically reduced depending how often you run it.