Tchaikovsky - Symphony No 5

When I first started listening to classical music I rather stupidly gave Tchaikovsky a wide berth because he was "popular" (think 1812 Overture and Swan Lake). Later on I got to like the Sixth Symphony (Pathetique) and the Violin Concerto, so I was expecting to like this. But I really didn't, I found it turgid and boring. A bit like early Sibelius without the sparkle. I'm trying to work out why. I think that maybe it was because Tchaikovsky was trying to express really extreme emotional states within too rigid a tonal framework. Mahler is, of course, emotional, but his freedom with tonality gives him the language.