While I'd agree that's a major issue for most the Americans I feel Brooksby is cut from a different cloth than the others. He likes cat mouse points. He gave Djokovic all he wanted for the first couple sets in the US open playing long rallies before he just was exhausted. He actually needs to develop some of what the others have. Needs a bigger serve to start
Agree his serve for his size needs more pop or else he needs to develop a better action serve with placement with a good second ball to push his opponent out of their comfort zone.
He is definitely more willing to grind, but the problem (for now anyway as he’s lucky these two are near the end) is that you can’t out grind Djokovic or Nadal (although I think Nadal may finally be hitting the end here). To your point about Brooksby, needs to develop the finishing power. However, as I noted it’s all about point construction, which is why Federer could still bother Djokovic and Nadal despite his age. Serve placement and attacking, constructive play. Nadal and Djokovic are the ultimate grinders yes, but they don’t just hit endless balls without purpose. They are both pure genius at using each ball to set things up. They are the two best players to go from defense to offense in one swing.
Brooksby is a taller version of David Ferrer right now where the dude can play long baseline points all day. But it only gets you so far, and having David Ferrer’s career is no shame at all. But if we are talking winning a slam, you have to have another gear to your game. Because as you noted his stamina isnt there yet to do that for a whole slam tournament and be standing at the end. I think he has the chops to do it, and I think he will get his game to that next level.
Fritz did that where he has really tried to work on his game despite his size. American male tennis I am praying is back on the upswing with a few of these guys we are talking about. And again, it will be a hell of a lot easier once Nadal and Djokovic are gone.