I'm building a "mail merge for PowerPoint": - https://pptxmailmerge.com

Still in MVP mode - but it already made some sales.

What's different about it from similar solutions is the way you can get data from an Excel file (most other companies have the JSON and CSV figured out).

It supports Excel style addressing so it's pretty flexible on how you reach for the data inside a PowerPoint template (access every sheet, every cell, named range or table to use it in merging process).

People use it for various kinds of use-cases - creating certificates, automating pricing offers, delivering employee feedback forms, preparing market research presentations and even subtitles for a theatrical play.