Read only access

I am looking for the way to setup read only access for operators. According to what I found in this video:

https://experienceleague.adobe.com/en/docs/campaign-standard-learn/tutorials/administrating/managing-user-access-rights

it should be achievable. However, using the setup described in this video my operators still can create, modify or run elements on the instance. I tried to set different parent units and even keep it empty, but still the outcome is the same.

Does anyone know how to achieve read-only access?

Thanks,

Dominik