Their output declined badly in the latter half of their run. The first three albums are absolutely terrific and there are still a lot of excellent singles on the next few, but after that it’s just like a band trying to be the Tragically Hip.
And so in a way, the Hip are, to me, both sides of this question. For eight to ten years they were insanely great, producing a wild number of wonderful songs, and for another 15, they were widely regarded as a national treasure even though none of their music was actually very good and I couldn’t make it through many of those later albums more than once. “Road Apples” is one of the greatest rock albums humans have ever recorded; “Now For Plan A” does not have a single song that can be described as interesting, original, well written, or anything else positive - and yet it sold like hotcakes, 'cause “Tragically Hip.”
Musicians run out of ideas at some point.