first 5 seasons was the whole story all another was added to make the serie run. season 3-4-5 the most important parts. If you like all this religious god demon staff etc is is good.
And yes the first season has a lot of crap
not exactly thefirst few seasons were all planned theres stuff in the first few seasons the corresponds with the 4-5-6th season after that it kinda on the fly but was still real good the first 5 episodes arnt even really part of the actual story