But they're others who want to play a different race for experience to get to know what it's like to play a different species.
You could start by designing that character in your mind - consider their background, culture, political and religious systems, etc. Of course, as soon as you see your character in a cutscene and/or select something from a paraphrase on the dialogue wheel, the character will likely do something completely out of character - but that's true anytime you're dealing with a highly cinematic game.
DA:O along with TES and Fallout games can give you that sort of RP experience, however.
Elves and dwarves and qunari aren't any less human either, but I think that their inclusion in DAI was an unambiguous positive. Whether they're human humans or humans in body paint and head prosthetics, I think it offers a high amount of RP value, depending on what the player is willing to bring to the table.
The very foundation of Dragon Age gave us the tools we needed to effectively role-play other species/backgrounds. Not only did DA:O give us origin stories - where we started out playing through the character's background - but during the course of the game, we also re-visited those locations and were immersed in their culture, religious beliefs, politics, etc.
The closest we've come to any of that in MEU were the ME2 visits to Tuchanka and the quarian fleet. Those were among my favorite missions of the series, because they were so rich with background and cultural lore. I guess what I'm suggesting here is that I don't feel like I know enough about any of the other ME species to effectively role-play as them. I suppose that could change, though, if the ME team ever chose to take things in that direction.
I don't understand why some posters (not you particularly) passionately and vehemently argue against its inclusion though. I had that fight months ago over many, many pages, and I still think it's very weird.
As near as I can tell, this usually boils down to a couple of different arguments:
1. The zots. Won't someone please think of the zots? If they spend the zots building a feature you would like, they will have fewer zots to spend on features I want. And if you think they should take zots away from MY content to invest in yours, then you're entitled.
2. It is incumbent on you to "prove" that the feature you're requesting is desired and would be used by a significant portion of the potential market for the game.
As near as I can tell, the whole deal with ME is that the protag is, and always has been, Bioware's character. Some people have complained (for example) about Shepard's relationship with Anderson, but Shepard was always written to have Anderson as a role model and father figure. We've also seen a lot of complaints about Shepard's reaction to the fall of Thessia - and again, it was Bioware's Shepard. People only notice these emotional expressions when they conflict with their own ideas about how the character might behave in a situation.
I guess what I'm suggesting here is that the expectations for massively effective cutscene emoting among existing ME fans might lead Bioware to continue to write the PC as their own character. I'm not quite sure how they could do that if they were to allow different species to fill the PC's shoes.