At a company I worked for in the last we had one of those homegrown systems to manage identity lifecycle

We couldn’t get rid of the managerial approval as that was needed for auditing and compliance, but the platform made it mostly self-service and automated

In the case of joiners, there were a specific set of permissions that were assigned based in the role they were joining at, and managers always had the chance to add/remove access before day-1

After that, the employee could use the self service platform to request access to other things they may need