At least when Vince feuded with Austin, it was made clear that it's an old boss who's fighting and Austin used to beat the **** out of him. Shane is booked as some sort of equal wrestler with those goofy punches to modern day main eventers.
He was apparently being "difficult" in the Rumble too, although how much fault can really be attributed to him? They dubbed him "the best in the world" then proceeded to have him beat up Kevin Owens, Miz, & other younger (by several decades) wrestlers. He was the ring leader of Raw Underground. He even roasted & demasculated Braun Strowman for a few months.
Of course he thought he could come in there and whoop Brock Lesnar
WWE really has no idea what they are doing anymore.