To a T is a puzzle adventure game developed by Takahashi's indie studio Uvula, and it follows the odd coming-of-age story of a boy stuck in a T-pose. When its trailer was first released, Ueda apparently reached out to Takahashi to ask him – "How do you play this game?" Takahashi remembers answering that the game didn't have any special mechanics – to which Ueda replied with: "That's great." The Katamari Damacy creator jokingly remarks that he thought "Ah, these are the words of a professional" when he first heard that comment. While Ueda's reply may not seem that serious at first glance, what he was actually trying to suggest is that current day games could benefit from focusing on more than just gameplay mechanics.
"While I don't know why I replied with 'That's great' back then, I was most likely thinking – The age of gameplay mechanics had already passed. I guess this is not the age to release new devices or offer new mechanics with each and every new game."
Ueda explained that, in his opinion, mechanics don't necessarily need to be "new" or "innovative," because the game's art and story are there to build the experience. "Even if there's nothing novel about the mechanics, you can push the game further with a certain vibe or artwork. Personal preferences aside, what I'm saying is – I think it would be better to give already existing game mechanics more definition."
If we take into account Ueda's previous works, the logic behind his reasoning becomes much more obvious. In his cult classic game ICO, rather than focusing on gameplay mechanics that would make the game entertaining and comfortable for players, Ueda decided to bring the art and the atmosphere to the forefront. Other prominent creators like NieR: Automata director Yoko Taro have praised Ueda's games exactly for this reason – by using already existing gameplay elements and deliberately ignoring playability in favor of conveying the message through the story and worldbuilding, the game ended up being one-of-a-kind experience for Yoko, and many others.

ICO, Shadow of The Colossus director praises Katamari Damacy creator's new game for not being mechanics-based. "The age of gameplay mechanics has already passed" - AUTOMATON WEST
Fumito Ueda praised Keita Takahashi's To a T for not relying on mechanics, stating that the age of coming up with new mechanics is long over.

I love Ueda and his works, but personally I couldn't disagree with this statement more.