Technically it was everything about the expensive hardware manufacturing costs which bogged the PS3 down during it's console race. The delay for the diode manufacturing caused some gamers to jump ship. Then the Cell architecture which needed more attention from developers and the expense to design/code games on perfectly. The developers especially Sony-owned first party studios however successfully harnessed it's potential.
Memory architecture seemed fine but not perfect in the long run. It was perfect for the time when console launched as XDR RAM module performances were highly praised around the time. As time progressed, many demanding multiplatform games had the texture streaming issues. But what more can one expect from a seven year old tech? The exclusives tried to outlive some of the shortcomings. God of War and Uncharted.
On the overall PS3 had so many other aspects which made it survive the current gen race which is worth the mention. It's library and online network service to top them off. I was thoroughly kept busy the entire gen gaming on it.
