3 hours is enough time to stand in line at the Louvre on a bad day in summer
Musee D’Orsay is better anyway but for 3 hours it’s a lot more suitable - the Q isn’t as bad - it’s better organised and you can see art rather than tourists. The Louvre is organised by filling every room to the brim at random then packing visitors in like sardines.
Sounds awful. 
We were last there about 12 years ago and didn’t experience anything like that.
I reckon we must have had luck on our side, that last visit was organised by our Parisien Club..
So many, many happy memories of Paris and its surroundings, introduced to us by those who had lived there nearly all their lives 
I literally was finding the link to say exactly the same thing. 
Lovely building, manageable size, so not too exhausting. Possible to look at a few superb paintings.
For a Paris morning of light and colour, I’d suggest:
Monet’s Water Lilies in the Orangerie - For me the culmination of Post-Impressionism - they’re also a great bridge between C19th painting and what was to come
Then if it’s a sunny day, walk to Sainte-Chapelle which is an exquisite architectural jewel.
But OTOH it would help our suggestions, if we knew a little more about your interests…
In july the Orangerie and Saint Chappelle would be nightmares! Both small and top trip advisor picks.
Back tracking a bit, Geoffre says he has about three hours to spare in Paris.
Which station do you arrive at?
I take your point, OTOH a couple of times I’ve been in Sainte-Chapelle on free Sundays when it’s inevitably crowded, but that’s not too problematic because unlike in an art gallery the main spectacle is above you.
Regardless of the specifics IMO there’s a lot to be said for visiting a couple of smaller places with a break in between rather than slogging round somewhere for two or three hours, with your eyes glazing over.
When I go to the Louvre, I spend time in this room:
I’m travelling by train (my first in France) from Angoulême to Montparnasse. I’ll stay overnight and take the Eurostar to London the next day. If the train journey goes well then I’ll keep the Louvre visit et al for a spring or autumn visit. But I’ll still try Notre dame and saint chappell.
Having just read Geoffrey’s comment, I was immediately going to recommend Raft of the Medusa as well. I saw it many years ago and it is definitely spectacular. And not the crowds around it like with some other, much less interesting paintings. Went to the Louvre last year but didn’t go to see any paintings, went to see all the ancient history exhibitions and was there several hours.
Agreed. IIRC it is directly across from David’s Coronation of Napoleon, which is one of my all-time favorites. That whole room of 19th century French art is impressive. I could sit there for hours.
Presumably it has Louvred windows…