Modern Team/Communication sites are not displayed on the classic create site page in Sharepoint together with other “classic” web templates. In order to create them you need first click App launcher icon in top left corner and choose Sharepoint link there:
It will open Sharepoint landing page which will have Create site icon on the top:
After clicking on this icon you will be able to choose which modern site to create: Team or Communication:
And on the last step you have to specify site name, privacy and classification (later one is shown if classifications are configured for your tenant):
After clicking Next your modern Team or Classification site will be created.