We see the entire combined galatic fleet pass a relay in seconds.
Yeah, I rolled my eyes when that happened. It was a blatant instance where "rule of cool" trumped lore. See also "thanix missiles" when the Thanix system consists of liquid metal accelerated to relativistic velocities and the Cain's projectile honing in on its target like a moth circling a lamp when it's described as essentially being a very big, very fast bullet. If you're OK with things like that, nothing I say will change your mind.
Had the Quarians not attacked there'd be nothing they'd have no time to flee from.
Except, y'know, Reapers, the second a couple of them turned up in whatever system they happen to be in. You're managing logistics for a flotilla of fifty thousand ships. If you're in the middle of food distribution, a drive-core discharge rota, or mining, refining, and distributing fuel from a gas giant (the kinds of stops which are absolutely unavoidable), you're not exactly in a position to pack up and go in the space of time it takes for them to pick a target and shoot. There's any of a hundred ways to get caught with your pants down, and if you lose a liveship (or a HE3 scoop, or a refinery ship, or...) you're screwed.
Needing a place to stay for their civilians (which I know is coming next) is bull.
I can already tell this'll be an entertaining rant...
For all I care, they park their civilian fleet on an uninhabited planet if they need a place to drop them off so the military fleet can join the Reaper war.
Dump them on some airless moon? Not survivable, especially in the event the fleet doesn't come back for them (which incidentally happens even if we win thanks to the destruction of the relay network). The whole idea is giving their species a shot at surviving the war while making their ships available to fight it. Disregarding their needs does them no favors.
I suppose you could make the ships available faster by simply spacing the civvies, but I don't think it'd go over too well.
Rannoch is not a necessity. They could even let their civilian fleet just float around somewhere between systems where they'd be relatively safe. Rannoch is not a necessity. It's not like they have to live on that planet or in between systems indefinetly. If the galaxy loses, it's irrelevant where they are, if the galaxy wins, Rannoch can be discussed.
Stop thinking purely in terms of shooters. Hackett specifically needs them as cargo transport. Logistics. The cruisers and destroyers are nice, but what they really need are the cargo holds which the Quarians currently have partitioned into living space across the civilian fleet. Before they can carry companies of Turian soldiers, levo food for Krogan fighting on Palaven, or raw materials for the Crucible project, the civvies (and the metal cubicles they live in) need to be cleared out.
By offloading on Rannoch, each of these ships only need food for the few dozen crew needed to run them instead of hundreds or thousands of additional occupants. The Turians could probably spare that much in exchange for the transport service they're providing; enough at least to supplement what the Fleet can manage to get out to them.
All in all, had they not attacked, Shepard and the galaxy would have had 2 full strength fleets for the war, instead of 1 or 2 fleets that have just come out of a war.
No, you would not have two full-strength fleets. You got no commitments from the Geth (who severed communication with their only outside contact after the Reapers invaded and before the Quarians did), and the other is severely limited in both utility and mobility so long as it's weighed down with civilians. This is not difficult to grasp.
Had the Geth chosen any other star system in their territory to build their sphere around and opened comms to the outside galaxy, this could easily have been avoided.