I think you got that a bit off. The rumor is [BLACKOUT] Cap leading a team without Iron Man, Hulk or or Thor that has Black Widow, Scarlet Witch, War Machine, Vision, and Falcon[/BLACKOUT].
And the people who keep talking about Captain Marvel and Hulk are missing the key thing. Thanos isn't gonna be the only opponent and it's unlikely a beat down will solve the situation.
Pretty much every single storyline of the heroes vs. Thanos has him holding his own against the big guns and only going down thanks to the intervention of someone else. He defeated the entire Avengers in his first major crossover and only lost because the half-dead Mar-Vell managed to destroy the Cosmic Cube while Thanos was distracted. His second major battle had him defeating and capturing the Avengers and even besting both the Thing and Thor, and only had him go down because Warlock turned him to stone after the rest of the heroes were beaten. Same thing in Infinity Gauntlet. He completely chumped the "big guns" like Hulk, Thor, Quasar, and Vision, and only lost because Nebula stole the Gauntlet while he was distracted. Then more recently in Infinity he was smacking around the likes of Captain Marvel, Thor, and Hulk, and was only defeated because Thane snuck up and trapped him in a state of living death.
There's a consistent thread in all of them: none of these fights are decided by "who can punch Thanos the hardest". He can withstand that. It's going to take more than that.