Let´s see if we can get one thing right. I've read books, seen movies, plays, where the end didn't tell you everything. "Speculation" was there at the end. But it was a good ending nevertheless. Why? Because some great writers did it. Some fantastic writing went on paper. Some philosophy was studied, some classics were studied, and some really good writers did it.
Did the ME3 writers team thought they were good enough to try that? Even if they could achieve it with more effort, did they really look at the ending and thought: "boy, we did it. We stood on the shoulder of giants and wrote the definitive "speculative" ending".
Where was the humility??? Didn't BW had anyone with guts to say: "hey boys, thanks for trying, but this is just not good enough?". Or try something different, that didn't hurt feelings, like: "well, no. Let´s keep this idea for another time. Let's try the more routine answer".