you can already do it, with Apple’s native Shortcuts app and Reminders app. You can set an automation to delete all reminders after a fixed time has passed with the ‘Remove Reminders’ action

Otherwise you can just use cronjobs with a small python snippet to parse and decide what reminders tagged with which labels to delete after X,Y,Z many days and hit the APIs of most major todo apps like todoist, asana, etc to just delete those tasks. Heck works with your local markdown based todo lists too.