"Doomstacks" aren't unrealistic. Concentration of force is a real military principle.
"Don't divide the fleet" is a naval truism.
You two are completely missing my point and it boggles my mind since I thought everyone who has played Aurora would have come to realize this:
Aurora VB6 forces players to stick all the ships in their TF/TG into a single point and keep them there. Doing anything else weakens your defences significantly. This is because how sensors and PD currently work. Usability of the interface plays its part too, as QuakeIV mentioned. The only reason to ever detach a ship from a doomstack was for it to take care of a cripple while the stack itself kept pursuing the enemy.
With the changes to sensors, the fixing of missile tracking bonus and the improvements to the Fleet Organization window, Aurora C# gives the impression that having escorts surround your capital ships and scouts pushed ahead and to the sides will actually be useful and improve your chances of victory, instead of being either useless busy work or actively harmful.
Doomstack is a term that describes the bad habit of strategy game designers to ignore their own game mechanics that lead to silly abuse of them, like in Civilization or Hearts of Iron or Stellaris, where doing anything else except a doomstack was to gimp yourself. I'm not talking about having one's fleet concentrated in one system, or waging an interstellar war in a single system at a time - that's perfectly fine. I'm talking specifically of the game play issue, caused by game mechanics, of having your entire fleet in a single point in space-time.