I couldn't imagine trying to get into Slayer now. Growing up in my early teens and playing guitar they were my favorite band for years and were the gateway to real metal for me.
Reign in Blood - Divine were incredible albums and yes Divine was their best album
Even the first two were decent, I was probably too young for those and didn't check them out until later, good for their time. I stopped listening to them completely when Diabolus came out and tried again buy buying God Hates, was disappointed. The title track was cool and they might have an ok song or 2 on those later albums but I just outgrew them I suppose.
But Rein in Blood - Divine are timeless
I don't care about theory, I do like music that fits and intricate riffs. Slayer didn't have much intracacy but they were ruthless, raw and agressive. I'm sure most children today can outplay Kerry, especially regarding his solos but most of the modern shredders today are fruity.
Everyone has this saying about James Hetfield having "the best right hand in the business". Jeff and Kerry would both eat James for breakfast.