Overtime activates when at least one player from the team with less progress stands on the point with time running out.

If you remove overtime completely then matches at some point are lost beyond saving when a team that can make a comeback doesn't have enough time to do so - it becomes needlessly intense.

Round ending as soon as all attacking players left the circle would just indirectly buff AOE displacement through the roof (Reaper LB, MCH shotgun, etc.). You can already win like this with a well-timed Reaper Hysteria, so thia wouldnt be fun either.

I wouldn't exactly add an artificial Overtime limit either for reasons like #1. Would make defensive stalling a bit obnoxious (Guard cycling) to deal with depending on your tools.

If anything, double or triple the respawn increases on death so it goes up by +3 per subsequent deaths. The trickle stall is what is actually annoying by it, so aim for that.