Weird thread, I own all three consoles, but really any of them could be viable as a primary gaming device. I mean, my iPhone would be perfectly viable as a primary gaming device. There is an argument for any gaming platform really.
That is exactly my point. Everything is subject to the individual's personal taste/needs. There are pros and cons to all three platforms. For example...
Many of the big 3rd party AAA games these days are starting to feel very samey and watered down. Many of them do not interest me as much anymore, and I find myself enjoying the AA games of the world more these days (which most come to Switch and portability plays a factor for me).
CoD for example released a solid game, but only after all of the positive reviews came in did they shove Micro transactions in our faces. Warframe is basically what Destiny should have been and now I can take it anywhere that has wifi with ease. Assassins Creed Odyssey, while a step in a good direction, has its own shallow issues and micro transformations to worry about.
I find myself enjoying games like Valkeria Chronicles and Ys so much more these days. There are of course exceptions, like RE7 or Red Dead 2, which is what I have my PS4 for.
My point is that any argument made against the Switch, can also be used against the others to some extent based on the needs of the gamer in question.