I would not call it a cakewalk, but it's still accessible compared to other games in its genre.

But we're talking 2D Mario, here. The last time a 2D Mario game presented a challenge necessitating any level of skill in order to beat it was arguably SMB3. So I doubt they're going to suddenly change course with this title. Especially given the direction of the last few games. Nintendo is about inclusion, and trying to provide a fun experience for all. Not challenging Ninja Gaiden NES fans. But we'll see. 

Zippo ... Huh ? That's a rumor not worth listening to haha.

Otherwise, despite the relative ease at which a 2D Mario can be played(the modern ones at least), I do expect as usual the challenge to ramp up in the last few worlds and even more so on the bonus secret worlds as is usual tradition. So you won't have to actively search for the challenge of you wish to

Zippo did predict some rumors tho, he predicted the 2D Mario, the sequel to 1-2 Switch, and 2D Metroid which would end up becoming Metroid Dread. He's been wrong in other instances tho and some claim he just piggybacks on other leakers' predictions. I wouldn't completely disregard him tho considering the stuff he got right

In terms of Mario's difficulty, I hope the game is definetely more difficult, Mario games in recent years became too easy in order to make the game accessible to as many people as possible, they're still fun games but I think they could definetely make it more difficult cause some Mario games are just too easy to go through outside of the very final few stage. I'll say the last somewhat difficult Mario game I played was Mario Bros Wii back in 2009.

It was Imran Khan who leaked the 1-2 Switch sequel. A new 2D Mario is also a veeeeeeery safe guess. Every Nintendo console since the DS had one, and on Switch even NSMBU managed to sell 10m+.

This is also the guy who said MK9 would be announced in 2022 and that a Chrono Trigger remake would be announced on the february direct. And that Golden Sun would be getting a Remake. And that Majora's Mask + Ocarina of Time would be getting a bundle for the Zelda 35th anniversary... The track record of the guy is terrible and at the end of the day even a broken clock is right twice a day. I doubt he's a real leaker.

I wouldn't mind if it was SMB3 levels of difficult. Nintendo's classic platformers are known for being difficult but for good reasons, instead of being broken messes like Bubsy 3D or Sonic 06.

If its hard as they say, it could be like NES Super Mario Bros games.