Currently, Secfix users are required to manually re-sync their IdP integration every time new employee joins or leaves the company to keep the list of employees up-to-date.

It can be automated. When automated, the admin of IdP e.g. Google Workspace would need to log in and connect SSO to load users only once, the connection then would stay up-to-date for weeks or even months. Only if the password was changed, the resync will be required to update the connection token again. (Maybe you saw it if you used Zapier in the past)