1 line, attributes from many polygons....

[ThomasColson]

I feel like this is a simple task with an obvious solution....but they don't call me Captain Obvious for nothing...

I have a line feature class for which I wish to attribute every polygon the line(s) pass thru. For example, a line passes through many states, I can, with automation, write the name of every state it passes through (with commas) to a text field. 

Can't be the first person to want to do this? 

[ClayDonaldsonSWCA]

this can be done with spatial join and the join field mapping!

Spatial Join (Analysis)—ArcGIS Pro | Documentation

Join	A concatenation of source values. You can use a delimiter to separate multiple input values.

[RhettZufelt]

As @ClayDonaldsonSWCA said, and here is a pretty good guide to that.  This is for ArcMap, but still the same procedure, you just have to hunt for the options in Pro.

R_