I don't want to derail the thread but I was only speaking as someone who regularly sees how false your misconception is on a daily basis. You can't get around that those are extra devices that have more or less thrived in a post-smartphone market.
I... don't see how that's true? Laptops, like all computers, have declined in sales since the smartphone and tablet markets took off. Global ereader shipments are like a third of what they were at peak -- much like a dedicated gaming device, a dedicated book-reading device is simply not as useful to many people who are happy to use a single multi-purpose device instead.
I think you're moving goalposts here. We're talking about viability in general, not "long-term" success, nor just in the West, or any vague ways you might be trying to calibrate the two in order to undermine what is otherwise common knowledge.
Again, not sure where you're going with this. The PSP was a pretty middling performer -- a success in blowing past expectations for a Nintendo competitor, and for its impressive second wind in Japan, but a failure in other global territories where sales fell off quickly and never recovered, and in creating a market position that its successor could take advantage of.
The kind of title you're citing was never successful once the novelty from launch wore off, and the lion's share of the PSP's most successful period in its most successful market was driven by teenager-oriented local-co-op games, not console-style titles. That particular market has been partially siphoned off by Nintendo, and there isn't even a hint of an opening for high-production-value, console-esque titles to succeed in other markets. Most of that has very little to do with Sony mishandling the device they did make and much more to do with them creating a device that couldn't really be handled well.