The tablet has to be more and more like a laptop if they want people who have a powerful smartphone to consider buying one.
The tablet market is shrinking, the laptop market is shrinking, and the desktop market is shrinking. The only thing that's growing is the phone market.
That's Cooks goal and he was quoted where he envisions the iPad ultimately being.
That said, the iPad is stagnant because those don't find a reason to upgrade their current iPad or tablet is plenty powerful and handles most tasks easily. The iPad Pro primary difference is the Apple Pencil and quad speakers, with an incremental difference in performance.
Where your post is not entirely accurate is the smart phone. Yes, it's growing, but a smart phone does not and cannot compete with an iPad or laptop. A smart phone is entirely limited on software for various tasks and does not serve as a bridge, as the iPad does for the laptop.
The iPad is ultimately consumed by the MacBook and MacBook is consumed by the iPad. Everyone differs on how they use their devices.
The iPad needs something big to re-ignite it and live up to Cook's quote.