I believe that to people like Magnus it goes beyond "the job becoming boring" and his stance alludes directly to Fischer's disillusionment with the game – lacking in genuine and human creativity.
It's not entirely surprising that both of these world champions saw that as a way to keep the game interesting.
Something else that Magnus sometimes does, even against fellow grandmasters, is play a completely ridiculous opening that's obviously bad. But more importantly, it's different, and all the existing opening theory goes out the window.
I read the above and it made me feel he was annoyed that Chess is a strategic zero sum game? "preparation and memorization than pure skill and innovation" - I think (at least in the zero sum strategy game I love) - prep + data IS the skill and innovation, how do you prep and where do you get your data, that's the joy of the game?
No, he's complaining about the depth of the decision tree at the start of the game.
So any variation that eliminates the need for preparation is a gain for both the winner and the loser.
And Magnus Carlsen is not a sore loser, he can both out-prep and out-calculate anyone in the world; hence the credibility of him suggesting that classical is not fun is higher than anyone else’s - because they could be called sore losers…
What's your game of choice, out of interest? I personally love Magic: the Gathering because it is a brilliant balance of preparation ahead of time, whilst rewarding quick thinking in game (with a fair dose of variance).