What does the OP mean with they "just can't re-invent themselves"? Since when is "re-invention" something that's a must have and if you don't "re-invent" yourself you're at a lower standard of artist?
There are iconic artists who dont need to re-invent themselves because their image and sound is so distinctive and respected that they dont need to change a thing. These artists shift albums.
Then there are artists who need to re-invent themselves in order to stay on top. These are singles artists.
Then there are artists who do neither...
Are you saying Madonna is a singles artist...? She's the queen of reinvention.
I don't get why people are being so defensive (well I do considering which stan base is the main culprit). No one said/implied it is necessarily a bad thing that they don't re-invent themselves. If it's working for you, why change? Just chill.
By re-inventing, I don't think we are talking about COMPLETELY changing, but rather adding on to their image and music, and expanding what they are about.
Rihanna, Lady Gaga, and Madonna are MASTERS at that. Their music and image is ever expanding, but they never forget who they really are. That is essential to longevity in my opinion.
Sorry but how has Lady Gaga shown that she is a master of re-invention?!