I suppose you don't have to go to the Louvre while in Paris, but it's such a huge structure that it's hard to miss.
I love museums, but I wasn't all that impressed with the Louvre. There. I admitted it. Said the unthinkable. It simply has so much and is so big that I quickly got burnout. A lot of the collection is artwork Napoleon (and his army) looted while he was terrorizing Europe, and even though the Louvre building is very grand, I had this feeling of being in a plundered booty warehouse.
After a couple hours of that, we strolled through the Tuileries and took the squirrelly nephews and niecelet to a carnival there. While they bounced off the walls of a huge trampoline, we sipped espresso at an outdoor cafe. I noticed a rainbow angle statue, and then a small rainbow flag on the espresso machine, and also a rainbow bear flag on the cooler. Hmmm. Was tempted to ask, but our (very nice) Parisian bartender spoke no English and my French is limited to "Excuse me, Madame, for butchering your beautiful language and taking your valuable time, but could you point in some vague direction that will supposedly get me to a bathroom? I'd be ever so grateful."
After we rested, the member of our party who knew Paris hiked us across the Seine to the Musee D'Orsay. He took us straight up to the 5th floor, where the impressionists paintings were displayed. If I had known, I would have skipped the Louvre and just gone to that museum. Monet, Degas, Van Gogh... it seemed as if every other painting was one I'd seen in an art book. It was simply the finest collection of art I'd seen anywhere. If I had to make the choice, I'd never set foot in the Louvre again.