"G" is becoming about as useful for identifying differences in mobile performance as "X" was for identifying CDROM speeds. As soon as marketers realized they could put any number they wanted before the X and outcompete their competitors, the number became useless.

Gs may be used and possibly overused in marketing but that doesn't mean that they are meaningless terms and "mostly marketing" as per my previous comment. Again, the terms are heavily used in the industry in technical and engineering circles.

"Even within a category such as "4G" there have been significant advances in some radio capabilities since it was introduced".

Yes but this is as I explained in my previous comment. There have been new features and new capabilities but on the same technology and system architecture. Think of improving internal combustion engines over time vs. switching to electric motors. That's how Gs broadly work on the technical side.

Perhaps the issue is marketing overusing a technical term that does not lend itself to it super well, especially when comparing 4G and 5G, from a smartphone consumer standpoint.