Drones of this speed only have a runtime of 5 minutes. Normal ones only 20-40 min
The hard physical limits of what drones can do given battery life are already being pushed, everything that does more radically increases unit price and weight.
drone “Swarms“ are already achievable, just have 20-30 guys operating as a team. The thing is they don’t because the real challenge is signals intelligence and battle tracking

This is the issue. Drones can sit and observe an area for 40 min, they can make a 30 km trip and deliver a heavy payload, and they can move fast....
But if you wanted 1 drone to do all 3 that'd be a $200,000 drone and it'd suck at all 3.
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And you need all 3 to actually kill someone, you need 1 to observe them, another to get out there really fast to intercept them, and you're compromizing on wieght to get there that fast so a slower one if you want a heavy payload.

The friction between these 3 goals is why normal infantry units can still operate at the front in their trenches for weeks on end.

There's no rule that says trenches have to be survivable if drones were as good as people say, infantry would just stop existing and the front would be drone vs. Drone with a 30km no man's land. That hasn't happened, because Drones are heavily limited