First things first: what an incredible piece of review work, Wesley! Smart, exhaustive, thoughtful and clear. Congrats on penning a "must read" for anyone considering a purchase of or even just interested in knowing more about the new iPad Pro M4.
No one can convince me that Apple is incapable of correcting the shortcomings and frustrations of iPadOS. I believe they continue to exist for just one reason: Apple's stubborn desire to have us continue buying two devices, not one. Not that many people aren't finding IPad to be the only device they need, but I am one of many more than that who'd be happy to ditch my Macbook for an iPad Pro but can't abide the frustrations and kludginess around simple common tasks like window and file management and multitasking.
I think the new iPad Pro M4 is one of the all-time greatest pieces of hardware ever released by Apple--stunning and a true hall of famer. But it has been met with uniformly tepid reviews like yours, not because of the hardware, but because, as you put it so perfectly, it's "hardware of the future running software of the past." Or, somewhat less eloquently, "like a Ferrari on a golf course" per Joanna Stern in her WSJ review.
I'll be curious to see what WWDC brings in the way of the next gen iPadOS. Is Apple finally ready to give us an operating system worthy of the hardware? Or will the bean counters win out yet again, looking at the 50% of Macbook owners who also own some model of iPad and deciding it's better to keep iPadOS hobbled than allow Apple buyers a genuine choice of one or the other.