Saying you can't please everyone doesn't really mean anything. I think we all know that, and Bioware knows it. This is the case for every form of media ever. Because it's basically a certainty, writers should write what they think makes the best story (but I do think they should take into account what their fanbase thinks makes a good story, even if it doesn't directly affect what they make - knowing your audience is important).
So the problem here is a difference between what part of the fanbase thinks makes a good story, and what Bioware apparently does. It's not about pleasing everyone, it's about being disappointed that a company could have such a drastically different view of what constitutes good narrative design than us, and in many cases, wondering if it's worth it to give this company more of our time and money.
And I should also reiterate that most of the pro returning-Inquisitor people are not people who clamor for each protagonist to return as the series goes on. Rather, this situation specifically has proven so important that is has made them do a complete 180° in opinion.
But what about the part of the fanbase who agrees with Bioware, or at least doesn't disagree with them? Isn't that the very definition of "you can't please everyone"? Those who disagree will always be disappointed, no matter the route Bioware chooses.
I, for one, think that Bioware's narrative design for Dragon Age is not only acceptable, but one of the things that draw me to the series. If suddenly it became another Shepard Effect (not that I don't love ME, but that series had its own narrative design) I know I would be disappointed, think it's a terrible narrative mistake that takes life out from the setting and wonder if I should buy the next game. Wouldn't it be a similar situation?
The difference is that, in my case, I could legitimately complain that Bioware had changed a narrative design that they have followed for 3 games already. Take it or leave it, it's a recognizable staple of the series. Like the prisoner in The Elder Scrolls (a narrative design I detest, but I know it's part of the deal and that many love it). They've never tricked the consumers in that regard, every game was marketed with a different protagonist.
If Trespasser didn't tie the Inquisitor's story properly, it's the DLC's fault, not the game design's, because it's always easier to adapt a DLC story to the game design than changing a game design spawning 3 games because of an epilogue not everyone bought. Despite current clamor, it's nothing very different from what could be seen after Witch Hunt and the much bigger cliffhanger ending of DA2.