No, you're not the only one, but you are becoming a minority.
Since Samsung created the phablet market, people quickly realized that there is no reason to buy - and carry around - TWO devices for the SAME purposes. Apple used the philosophy that you phrased above as their sales pitch for quite a long time simply because they did not have a phablet in their portfolio. Now they do, and strangely enough, nobody is saying "we think 3.5" is the perfect size for a phone" in an Apple keynote anymore. They actually have a hard time explaining why anyone who owns an iPhone 6+ should buy an iPad Mini - a device of almost the same size, but without phone features. I guess the iPod Touch market also has become a bit of a problem for them. And with Ultrabooks like the MacBook Air - a device that can actually be used for writing - there really is a question why anyone would need a tablet in addition to a notebook and a phablet.
All of that leads back to square one when those gadgets hit the market, and after all those years I still have not found any real use for them except for the use that they had back then: eBook readers, comic book readers, consoles for touch-optimized games (like board game adaptations) or mobile surf boards (as Jobs said himself, usually on the toilet or in the bed). And that's about it. And let's face it, most of the time a phablet is big enough for any of these use cases.
Back to the original topic:
I wonder if anyone in the last 20 years has ever said "this screenplay was entirely written with Microsoft Word". Or Scrivener. Or Montage. Or Final Draft. For some reason, this might be an interesting niche knowledge, but everybody knows that the choice of the tool usually doesn't make the end result any better.
Alright, granted. You raise some fair points.
I think the iPad Mini is indeed a dying product, just like the iPod Mini before it (entirely different deal of course). If not, it's because it's life is sustained by kids I'd say.
Regarding full sized iPads, well, there's my market group, whilst perhaps a minority, still an existing minority. Then there's the Android crowd, who seeks what you call "a console for touch optimised games", because Android just doesn't have the same plethora of games the iPad does, especially not on the same release schedule. And for gaming, I'd argue the size of the full sized iPad is valuable, but hey, I've got piss vision. 4-inch iPhone + iPad will always be my preferred touch device combo. Whilst certainly not a segment Apple focuses on marketting the iPad to, also consider elderly people, who perhaps have an old feature phone, and use the iPad for necessary computing, such as web. Add in the education market, and suddenly the iPad seems to have its market again, doesn't it? And with the rumoured iPad Pro further dividing the phablet from the tablet, I don't see tablets as a dying product category. Just one that is seeing changes to its market environment.
And regarding the last paragraph, whilst you are most certainly right to an extend, the tools with which we bring our thoughts to reality do matter. I mean, if you gave John Mayer my guitar, he'd still play it way the bloody heck better than me, but it'd still sound better if he played a better guitar... Or to make that analogy even more extreme, imagine my guitar not being tuned. Actually, in some cases, the tools bring the idea for the product. Continuing the previous analogy, even if it's perhaps not the best suited analogy for this, if there had never been guitars, John Mayer wouldn't know to play one.
