According to this wiki, write back on CDS view is not supported:

And also it is defined in ABAP help that only read operation is supported. For other operation like write, you have to still use original database table.

Test on write operation attempt

I have a CDS view Zp_Mara_Redirect and its corresponding database view is zmara_cds.
When I try to insert some entry to CDS view, I get following error message:

When I try to insert some entry to CDS view's underlying database view, still not possible either.

Once the database table is redirected to a CDS view, the database itself is not supported to be changed by ABAP code. See this example below:

Insertion failed:

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