I think, if anything, that one of the central problems with the ending is that the overarching story of the series, beside the main plot (stop the Reapers) has all these different running subplots, like humanity finding its place in the galaxy, the Geth and the Qurians, the Krogans and the Genophage, but the ending decides to ignore of all these, save one, and even fails on some levels to deal in a functional way with the main plot. The overarching theme that is to be taken away from the main plot and all the subplots this seems to be "intergenerational conflicts", something which is even reflected on a somewhat minor and more personal levels in some of the different Squad Members' personal stories and even in a few side-quests.
There is basically a whole spectrum of stories that are different reflections on the theme of "intergenerational conflicts", but the kicker is, that the last 10 minutes isn't about this spectrum, and doesn't seem to care about or even want to be about the spectrum. No, the last 10 minutes suddenly decides that it, and retroactively the whole series, is (or rather should be) about this very specific subset of "intergenerational conflicts", which is "synthetics vs. organics", and seemingly just it can throw around some high-faluting, pseudo-profound ambiguity about the singularity.
The only content in the series that seems to fit this idea of "synthetics vs. organics" as is presented in the last 10 minutes, would appear to be the Geth and the Qurian subplot, but the player has at this point already resolved this plotline some hours ago, yet here it the question is blatantly regurgitated by the Catalyst (albeit in a somewhat altered form), without any acknowledgement of how the player answered it earlier, and what the player has been shown about the motivations of the Geth, doesn't fit the way the "synthetics vs. organics" story as it is presented by the Catalyst.
