A Nintendo insider is claiming that Super Mario Bros. Wonder is accessible to everyone, but Nintendo ramped up the difficulty quite a bit.

So, anyone here thinks this will be a harder Mario game? Does this insider sound believable?

Zippo is not a reliable source, even when it come to leaks. I wouldn't give much thought to it.

Hope it is hard and lot of secrets !

There's no way this game is not going to be accessible to everyone. Perhaps they will include a difficult setting, where veteran/skilled players can get a good challenge if that's what they want, but that's about as far as current Nintendo will go.

That or characters control differently and have different abilities.

I do hope it has some challenge to it. It's a Mario game though, and I believe the last difficult console Mario game was Yoshi's Island on the SNES. I wouldn't expect to die nearly as often as say Donkey Kong Country or Celeste.

Then what about Tears of The Kingdom released just this year? You think it's a cakewalk?

I'm up for a challenge, but as long as its not like the crazy stages like Mario Maker where you have to pretty much play perfectly to get through it lol

*Arin Hanson's screams heard in the distance* XD

Pretty much this. I think Nintendo does a good job on this with Mario titles. Generally the first 5 worlds are pretty smooth sailing for experienced gamers, you start losing a life here and there in worlds 6-7, world 8 actually gets you frustrated a few times, and then the secret bonus worlds get into controller throwing territory at times. Maybe they'll do a DLC kind of thing offering a more challenging campaign. Super Luigi U was noticeably more difficult although not on the level of something like DK. 

Fairly sure they meant in the context of a Mario game.