Why didn't other heroes use the Gauntlet while they were playing catch with it?

There's now an interview confirming that basically, only Hulk (and Tony) could do it. You have to remember that the Gauntlet is equipped with all six Stones at that point, which is a whole lot to handle. Even Captain Marvel might not have been able too, and she's easily in the top 3 of overpowered people in the MCU.

Sure, that interview only talks about the "final" snap, but it's probably valid for partial actions as well - in the heat of the battlefield, you won't stop to take a Stone off, fire part of a power, reslot the Stone... Sounds like a nice way to lose one, which would jeopardize the overall plan of "in the end, use all six and unsnap".

Q: Why Iron Man has to be the one to do the final snap, couldn’t the people like Thor, Star-Lord or Captain Marvel whom all previously have handled the power of Infinity Stones done it instead?

A: Thor in this movie couldn’t do it, only Hulk was strong enough to do the snap without dying. We are still not sure whether Captain Marvel can also withstand all the power of Infinity Stones at once. The reason we choose to let Iron Man do it in the end was because he was the closest one to Thanos at the time. In all the futures Doctor Strange foresee, Iron Man was the only one who could get close to Thanos and do the snap.

'Avengers: Endgame’ directors just explained some of the movie’s biggest mysteries, BGR, April 30th, 2019

Many of these heroes saw Professor Hulk put the gauntlet on and get his arm cooked. Likewise, many of these heroes know that using the stones unleashes a fatal level of radiation that will kill any mere human, regardless of what technology they wrap it in.

Nearly all of the heroes that have followed the cinematic universe this far are aware that only super powerful beings are able to hold individual stones.

There is also more to it than "sacrificing themselves" - they're well aware that the problem of Thanos killing half of the universe doesn't end until the stones have been returned to their own timeline, simply using the stones doesn't guarantee that they're going to win and Thanos has already changed the game - his next snap isn't going to kill half of all life, it's going to kill all life and then recreate half of it. This is the last chance. There's no room for mistakes.

So - why didn't they use it? Because it wasn't the plan. The plan was:

• Hulk snap
• Return stones to their original times