The Filter Cannot Complete Because More Than One Object Is Selected -

Similarly, a applied to a group of text letters would warp each letter around a different center point, creating illegible chaos. By forcing you to select one object, the software ensures the filter has a single, predictable reference point.

Next time you see the error, don't curse the software. Expand, compound, or rasterize—and move on with your design. Similarly, a applied to a group of text

From a programming standpoint:

If you don't need vector editability, flatten the selected objects into a single raster image: don't curse the software. Expand