The next symphony Bruckner wrote was the 'official' Symphony No.1, called by Bruckner 'the saucy maid' (whatever that may mean). Then it was the Symphony No. 0 in D minor that was written in 1869. Bruckner rejected this symphony after some harsh criticism and wrote on it the empty set symbol ( Ø ) which was later interpreted as the number 'zero'.
After all that, why bother with an early symphony that the composer himself rejected when he wrote so many more? Bruckner was known to be influenced a great deal by the opinions of others, especially early on. To my mind, if Bruckner would've wanted the world to never hear of this symphony he would have destroyed it. And it's a good thing he did not destroy it, for the symphony already shows his mature style and the music is very good. A composer's earlier works are always interesting, if for no other reason than it shows where they came from and how they evolved when compared to later works. Bruckner almost from the beginning had different ideas that grew into his mature style. Deryck Cooke writes about the Bruckner Symphony:
"Despite its general debt to Beethoven and Wagner, the "Bruckner Symphony" is a unique conception, not only because of the individuality of its spirit and its materials, but even more because of the absolute originality of its formal processes. At first, these processes seemed so strange and unprecedented that they were taken as evidence of sheer incompetence.... Now it is recognized that Bruckner's unorthodox structural methods were inevitable.... Bruckner created a new and monumental type of symphonic organism, which abjured the tense, dynamic continuity of Beethoven, and the broad, fluid continuity of Wagner, in order to express something profoundly different from either composer, something elemental and metaphysical."