I'm shocked that they caved to the pressure. But ultimately that pressure came from their customers, so if the vast majority are actually dissatisfied, and not just a vocal minority, it's smart to give them what they want.
*spoilers obviously*
Personally, I was only mildly disappointed by the ending, but there was a lot that I liked about it. I thought the leadup was engrossing including all the last bits on earth and the confrontation with the illusive man. And the ending did a nice job of finally explaining what the Reapers are, aside from unsympathetic death robots. I even like how you were forced to make an unexpected and difficult choice that involves huge sacrifice whatever you choose.
And I certainly don't need to know what happens to every character for the rest of their life, I hate endings that try to do that. What bothered me were the inconsistencies. Why is EDI still alive when I choose to kill all synthetics? Why was Joker joy riding through mass relays when the final battle was taking place?
Also, I would have preferred that the ending be determined largely by my actions throughout the game and even previous games, not just a choice foisted on me at the end.