True, the Atari 8-bits did not come with developer docs and in the early years little information was available. This certainly hurt its initial adoption.
But starting with De Re Atari by Chris Crawford in 1982, a lot of development material became available. Compute! had a great line of books, including Mapping the Atari.
It was shame it took so long for that material to appear because the Atari 8-bit have a rather elegant OS, especially compared to its contemporaries.