It seemed to me to be leading us towards a Reaper Invasion and into conflict. At no point did it give me the feeling that we would lose, because no matter how bad the situation might be there is always the chance of winning.
I can think of many reasons why the reapers would not win.
I can't. Not if you're talking conventional victory.
The Reapers built the Mass Relays. The Mass Relays, as evidenced by Arrival, are capable of being blown up to wipe out star systems. That means the Reapers are capable of constructing Supernova Bombs.
If the Reapers registered us as a threat - a real, bonafide threat, which was more important to wipe out than harvest - they'd wipe us out. And we wouldn't have a say in the matter. The only reason we're alive in ME3 is because they want us alive. If they wanted us dead, we would be. TIM correctly points this out during the conversation on Thessia.
Conventional victory was never on the table. Imagine that the Reapers decided we were too dangerous to be left alive:
Our fleet jumps into a star system? Supernova bomb.
They find one of our colonies? Lure us with the prospect of evacuation, then Supernova bomb.
We retreat away from the Relays, and do our best to disappear? Distribute a network of Occuli across the galaxy. One of them detects us? Supernova bomb.
We never settle on a planet, keep on the move, and never hang around long enough to gather resources because of the risk of supernova bombs? They just have to wait for us to starve.
You get the idea.
The Reapers could sterilise the galaxy, give up on harvesting our cycle, and wait for the next one. The Catalyst downgrades the length of time between cycles so that the next species aren't so dangerous, then resets the trap and sends the Reapers back into Dark Space. Heck, something like this probably actually happened at some point in the past.
Frankly, compared to Sovereign in ME1, the Reapers seem to have been nerfed somewhat for ME3, and we still didn't stand a chance without the Crucible. We needed something that dealt with the Reaper problem - and dealt with it quickly - so that they never even had the chance to consider us a threat.
So while I agree that the Crucible plot was handled badly, I don't dispute that something like it was necessary for ME3. (I've said it before, but I'd have gone with the idea that the Reapers themselves were indoctrinated, and have us develop something that releases them to fight amongst themselves.)