Scriabin is one of the most important composers in my life. When I truly began studying him, it became clear to me that his music is quite esoteric. The 2nd sonata as you pointed out, is of course a beautiful work, and I believe if the majority of his compositions followed that style he'd be more mainstream. However, I suggest listening to works like sonata no. 6, Prometheus, poème nocturne, op 65 etudes. Essentially works after opus 50 even, and maybe the unique style of that era of his music will shed light on why he isn't not necessarily appreciated, but just not understood. He is a very acquired taste. Also if it's any consolation, his music is highly respected in Russia and he is just as famous as Rachmaninoff there, and if he is less well know now, it should be known that at least in Russia he was very much a household name during his time. Also Rachmaninoff performed his music all over the world when he passed In memory of Scriabin and had an extremely deep respect for his unique music which was influential on rachmaninoff himself. Read Scriabin's bio by Faubian powers for more insight on his life too!