The way I see it, the intent here was never to come up with replacements for existing products, but to use personal technology to come up with alternatives to more powerful computers.
Key word here is "alternative", not "replacement". For example, I use the iPad to complement my classroom teaching not because it was strictly better than my school-issued laptop in every sense of the word, but because it was better at the things I needed it to be better in (and the areas my iPad Pro was lacklustre in turned out not to matter in the grand scheme of things).
In other words, I love my iPad Pro precisely because it didn't try to hard to be a better laptop, which in turn freed it up to shine in its own unique areas. Areas that a conventional laptop suck in. Your argument hinges on the assumption that the laptop was already the best tool for the job for everyone. In reality, it wasn't.