Hi Lilian,
Thanks for posting in the community. We are happy to help you.
Per your description, for "all team members can make … in their personal oultook", I assume you mean that they can see this calendar in each member's Outlook desktop application and can make an appointment/meeting.
If not, please point it out and let us know.
If so, there is a way to meet your needs. You need to create a SharePoint calendar and let users sync the SharePoint calendar to their Outlook. Since the SharePoint calendar is stored in SharePoint, it remains even if the creator leaves the company. Here are the steps.
- Create a SharePoint calendar in SharePoint.
Go to the relevant SharePoint site, Settings, Site Contents, + New, App, classic experience. Select the Calendar app, name it, and click Create.