How about downloading the previous version of the module (5.0), which is fit for 5.9.1?
A workaround might be to handle the import of a CSV file in a microflow:
Create a filedocument and open a popup. Use a filemanager to upload the CSV file. Once uploaded, you can call a microflow the handle the import. In that microflow use the java action "StringFromFile" to change the filedocument to a string. In the microflow you could use the string to map the CSV to your entities and attributes.
It requires some modeling in your microflow, but in the end you are able to import the CSV file without the flat and delimited module!
Hope this helps!
You could use the Excel importer, however this is only for excel files. So this means the .csv should be converted to excel.
Is it no possibility to upgrade your project?