So we are pretending Shep didn't get tons of help from Garrus, Liara, Tali, Mordin etc?
Shep didn't defeat the Reapers by himself/herself, wnd more than likely would have failed without his alien friends.
Lets take a look at that help you mention
If Jack isn't alive in ME3, Prangley will always be killed. Why couldn't Liara and Garrus, if he's alive in ME3, provide cover fire while Shepard helped Rodriquez get to the shuttle? If that had happened, Prangley most likely would've lived.
When facing Ashley/Kaidan during the coup, Udina says Shepard is with Cerberus. Why couldn't Liara and Garrus speak up saying that Shepard is not with Cerberus especially since a lot of them have been killed. All they did was stand there with their tentacle or claw stuck up their fifth point of contact. Had they of spoken up in support of Shepard, Ashley/Kaidan may of lowered their weapon and avoid being shot.
When rescuing the ex-Cerberus scientists, Shepard is knocked to the ground. Who do you think it was that helped Shepard back on the shuttle? That's right. It wasn't Liara or Garrus or Tali. It was Dr. Cole and to provide cover fire, it was Jacob, if alive, or Dr. Webber. What was Liara and Garrus and Tali doing while this was happening? Lets ask them.
Garrus: I was calibrating something
Liara: I was taking armor from dead bodies.
Tali: I was getting drunk
The funny part about that is Tali, Liara and Garrus are potential love interest. If I was to romance one of them, I would break off the relationship and kick them off my ship. What's the point of having them as squadmates if they don't have my back?
Tali wasn't needed in ME3 unless you wanted peace. But her just standing around doing nothing while the geth uploads the code was pathetic. She really never cared about her species. I give her high marks for the nice swan dive.
With Mordin. Yes he was helpful especially in ME2, but he was not needed in ME3. Padok Wiks did the same thing and fortunatley he was nice enough to not cure the geneophage.