Hi Ed,
Unless Apple has revised the business card template recently, the document created from that template does not include a Table. It is composed of a set of graphic objects and text boxes repeated 10 times on the first page (and a similar set repeated 8 times on the second page. Here's an example, using the "modern business card" template from Pages 5.

As can be seen in the upper left set, where all elements are selected, each 'card' has a graphic object (which is actually a Grouped object, made from three small squares, each filled with a different colour), and two text boxes, each containing placeholder text.
Click once to select one of the text boxes, then click once in the 'name' text to select that placeholder text, then type the name.
Click once in the job title placeholder, then type in the job title.
Repeat with the second text box and the phone, email, street address, and web address information.
Copy the contents of the first text box, then paste it into each of the others in turn.
Repeat with the contents of the second text box.
Not a lot of automation (even less than with the table approach I suggested), but it does give you some basic design, and a layout that fits available Business Card stock from Avery or other suppliers.
As for the table approach, the complicated part is setting up the table to begin with. Most of the complication in my description above was in avoiding sowing a page filled with error triangles. Here's a rewrite that avoids that struggle:
The image shows three copies of the same table at different stages of the process. It does not include the initial step of setting the row heights and column widths as described above.

Image 1 (top):
With the column and row sizes set:
- Click once on cell A1, then type = to open the formula editor.
- Enter the formula shown ( $A$1 ) and click the green check to confirm the formula and close the editor.
Ignore the error triangle in the cell.
- Using the Fill handles, fill the formula right to C1, then down to the last row of the table
All cells will contain error triangles.
A1 is due to the formula in that cell referencing its own cell.
The rest are due to their referencing a cell (A1) which contains an error.
- Click once on cell A1 and press delete to delete the formula in that cell.
- Display in the rest of the cells will immediately change to "0" as seen in image 2 (middle)
- Enter the desired text in cell A1.
- The text will be automatically reproduced in each of the other cells.
Once set up, you can change the text in all cells by entering the new text in cell A1.
Limitations:
Text in a single cell in Numbers must all have the same format properties. Changing type size (as done in the upper text box of the Business card template) or other attributes of the text is not possible within the same cell.
Images and other graphic objects may be placed in table cells only as Image Fill, which automatically resizes to fill the cell.
(Images can be placed behind the table, though.)
Regards,
Barry