I think it depends on the specific use case and type of content. For example: a
Content Type can be defined such that it contains rows and columns in which you arrange a series of fields in rows or columns that can allow a user to drop in file content. An example of how that might be arranged is below:
If the question is just "can a Content Type contain other Content Types," then you might be able to achieve this with the
Block Editor field, which can be configured to render arbitrary user-defined content, by selecting "Contentlets" on the interface and then navigating to the content in question.
Does something like that fit the bill? If not, what would be an example of the kind of end user experience you're envisioning?