"10 years ago" would be the time of transition from Pages '09 to Pages v5.x. Here are the Table menus from Pages '09 (v4.x) and Pages 5.x:
Pages '09:
Pages '09 included this item. Greyed here as no Table was selected when the screen shot was taken.
Pages v5.6.2
The menu item was not included in this version of {Pages, or any version since then.
"OK, I've got a table set up & filled. But now I need to make it as 'flat' text."
Assuming that the "flat text" qualification can be satisfied with 'the contents of each cell of a table, expressed as text values, with the contents of cells in a row separated by commas* and rows separated by a new line control charater", ther conversion can be done by exporting the file to a txt file.
In the case of a file containing more than the table, it might be necessary to copy the table and paste it to a new (and empty) Pages document before doing the export.
Another tactic would be to select all cells containing the text you want to convert, then using Paste and Match Style to paste that text into a table-free space in the receiving document.