That might be something you can do using a Dataflow into a Dataverse table. In a Dataflow you can use the power query to get files and then format the data to put into a Dataverse table. Power query can be helpful with some clunky outputs and putting them into a format you want if you know how to use it.
You could then use a PAflow that triggers like when you add a file to a folder, and within the PAflow is a trigger to start the Dataflow which will go into the folder and get the files and format them an put them in a dataverse table, when the Dataflow is complete it will tell the PAflow which would then call the data from the Dataverse table to put into your SPList. Also in that PA flow you could delete the document from the file folder so that next time the Dataflow isn't rerunning all of the older files (you could leave all the old files, but it will make it slow).
This probably seems like a lot of work, but that's what I would do since I'm comfortable with using Power Query and Dataverse.
Also worth a shot talking to your IT or software provider about upgrading that report maker so you can at least get raw data instead of some clunky old Dot Matrix Print format. The irony is that the data is stored somewhere in tables how you'd like to see it, but it gives you a terrible output, when it would be easier for you to just access the tables directly.
Are you manually downloading each excel file? Or is it generated automatically as an output of some process?
