Because that "time past" were the "Last days" (last days of the old covenant). I do believe that was a unique time (all the physical healing, for instance) but that doesn't mean the Holy Spirit has ceased to guide and teach us....to stop leading us into Truth.
People can use Scripture (including pastors)....but only the Holy Spirit can "teach" or lead us to wisdom. Truth can be found in many places....many sources (even a donkey spoke Truth). Likewise....lies are also found in many places and even through unlikely sources. People can speak - in one sentence - a mixture of lies and Truth.....and only through our devotion to desiring to know the Truth through the Holy Spirit (abiding in Christ)can help us to decipher that.
I don't believe any one person (other than Jesus) has ever been the holder of all Truth....and it's idolatry to rely on any person to decipher what's True and what isn't.
James 1:5
Now if any of you lacks wisdom, he should ask God, who gives generously to all without finding fault, and it will be given to him.