Hockney can change all he likes, he is a sub-standard artist, regardless of popularity. Though there is at least more than a modicum of talent in his bones, which is more than can be said for the embarrassing Tracey Emin and the factory that is Damien Hirst.
Kandinsky is a wonderful artist - I went to an exhibition of his in Milan 6/7 years ago where they lit some of his canvases from behind and above - unique and mesmerising. He has written some very well-regarded books on art Theory
http://www.amazon.co.uk/Wassily-Kandinsky/e/B001HN1EFE/ref=sr_ntt_srch_lnk_1?qid=1417720279&sr=1-1
I don't particularly like Gaugain either, but it's hard to evaluate that period of art objectively as we have been so over saturated with it.
Rothko is very interesting, and that room in the Tate is indeed very nice (is it still there?). I see the Tate are extending? They would be better off improving their collection rather than enlarging their space - they have some fantastic individual works (de Chirico, Braque, Kandinsky, Picasso and even some Max Ernst if that is your thing) but as even the awful Nic Serota says himself, the collection is second rate - the space has become overrun with tourists and wannabes which could be frustrating, but it leaves the NG (what a collection) easier to manoeuvre, especially away from the impressionist works - incredible to think it's easy to 'have' the Caravaggios to yourself yet 50 monkeys crowd around a burnout car in the Tate Modern! The TM should look to do a deal with the Centre Pompidou - despite the fact there is a second Centre Pompidou in Metz, and they loan generously, the amount of first class works in storage facilities is shocking (I know someone who worked there). Finally, on the TM - their exhibition prices are a disgrace - 17£ for Matisse! I am a member but the average person who doesn't have a huge disposable income is priced out of this.
There are some great expos in Paris this Winter - Duchamp's paintings at the Centre Pompidou (have been twice but will go back) - from a theory of art perspective it invites you to read a lot about the early 20th century. Sade at Musee d'Orsay too. Saw a small exhibition at Musee Delacroix, and have Perugino, Gehry, Delaunay exhibitions to see, as well as one on the Collabos of WW2 which should be interesting.
Moehat - do you read much on Art?