Treatment of 1st column in a chart selection

This, IMO, is the definitive essay on how Excel decides when to use the first column for x data and when to include it among the other data series: https://peltiertech.com/good-chart-data/

For your purposes, I suggest paying particular attention to the "First Column Different: Top Left Cell" section. The easiest solution I can think of based on your example is to clear A5, create then chart, then enter "Age" in A5 after the chart is created.

Back before version 2007, versions 2003 and earlier prompted you with a "chart wizard" series of dialogs that did allow you to override Excel's defaults during chart creation. In the "upgrade" to 2007 (and, apparently, version since then), they have never felt a need to bring this feature back.

I guess I'm just agreeing with you. I, too, think there ought to be a better way to create a chart that allows the user to override Excel's default decisions. As Excel currently stands, it seems that MSFT wants us to create the chart with Excel's defaults, and, if we don't like Excel's defaults, they prefer that we "fix" Excel's mistakes after chart creation. I'm not sure why MSFT wants it to be this way, but that's what they've given us.

Sometimes I wonder if the best solution is to use a spreadsheet other than Excel. I don't particularly like Google sheets chart engine, but I find that LO Calc's chart engine is workable, and it uses a kind of "chart wizard" series of dialogs that allows you to specify what you want to have happen while creating the chart. Of course, that assumes that you are allowed to use a spreadsheet other than Excel.