I think In Exile is totally right about just everything.
To me, the ME3 suffers from being too vague in its early-established plots, like how weak are the reapers? They obliterate literally everything they come in contact with in Vancouver, yet Anderson thinks earth has a chance and he takes a shuttle right in the hotzone, when he could've taken the Normandy and be dropped off in a place that wasn't overtaken.
The way the characters talk about the reaper invasion is often as if Reapers are a force equal to humans or civilized aliens of Milky Way, and not these Godzillas that stomp is like ants and all we can do is escape.
The crucible has several lines of dialogue in which it's mentioned, early on and late in the game, but it switches back and forth between whether it's known to be a weapon or have a completely unknowable function.
You can feel how the writers iterated on these things, but never came up with a consistent definition for either case. In the case of both the reapers undefined strength and the randomly shifting beliefs regarding the crucible's functions it makes for really weak and confusing character motivations, so at the end of the day the plot just doesn't feel believable enough.
If ME3 was true to the lore, the game would last two hours(tops) after Reapers took the citadel and gained control the entire relay network as a consequence of ME2 being a giant waste of time(more so if one was an idiot that destroyed the CB).
The writer(s) must've known they dun goofed with ME2, which is why the Reapers' strategic sense in ME3 is on par with a four year old girl's, the tidbit of the Citadel controlling the relay networking ending up quietly ignored, and the introduction of the derpcible. They also completely retconned the protheans' destruction as well, Vigil in ME1 made it clear they were doomed the moment the reapers came out of the citadel and with the rest of the "war" consisting of reapers picking off isolated prothean worlds, but according to the walking retcon in ME3 that's Javik, they claim the Protheans actually put up a decent fight(lol).