Your question about why Deckard must be a replicant has been answered by others in this thread. As to how Roy got to see Tyrell - Tyrell invited his chess partner J.F. Sebastian to come in and Roy tagged along.Big Orange wrote:Blade Runner is not awful, but I find Alien (Ridley's earlier effort) much more watchable and entertaining - Blade Runner has that unique feel and Rutger Hauer kicks ass, but I feel it has few minor plotholes that even the Director's Cut does not fix (why is Decker supposedly a Replicant clone? How did Roy Batty enter Tyrell's inner chamber in his massive pyramid headquaters?).
In regard to the OP - simple answer - you either grok this movie or you don't. Longer answer - people differ in their tastes and perceptions, plus it also seems the younger generation has many who have a different perceptual space to older fans in regard to some classic movies (& also new movies). In the future you may come to appreciate this movie.
Both the Director's cut and the one with the voice over have advantages compared to the other.