Fair bit of hyperbole going on here, as expected.
Some of it could maybe be improved, but it’s nothing like the Mass Effect 3 debacle.
There were some quirks, but I enjoyed act 3.
Can you explain how it is any different from the Mass Effect 3 ending situation? If you're being honest to yourself, it's exactly like it. ME3 was trashed for its ending because unlike ME2, your decisions didn't affect the ultimate conclusion of the story which was instead boiled down to an extremely rudimentary choice between control, destroy (sounds familiar?) and synthesis. This was controversial because ME2's ending had a lot of variance based on your approach to companions which also tied into the morality system of that game and people expected ME3 to live up to that standard if not to surpass it. Arguably, ME3's ending was still better than what we got in BG3 because your Alliance military strength (which was a sort of score that was calculated based on your choices and side quest completion) could affect the ending. No such mechanic exists for BG3. It's more or less a simple binary choice.
I sure can. In Mass Effect 3, whatever choice you made, you were treated to the EXACT same cutscene, with the literal only difference being a different colour effect on the relays. There was no dialogue with your companions, because you were gone. Nobody commented on what happened or what comes next for them (it was implied that they were marooned).
In BG3, there is dialogue with your companions. The choices you made throughout the change what they do next, and in some cases you can try to convince them otherwise.
Also the war score thing was much less fun than calling the allies you made, made even worse by the fact that the best war score results were originally unachievable for people who didn’t want to get involved in multiplayer death matches.