So for the longest time I've been disappointed in Garrus' ME3 treatment because he is just a yes man tag along to Shepard. For a roleplay run I'm doing I had Garrus be the lone casualty on the Collector base mission after not recruiting him in Mass Effect 1. Playing 2/3's of the trilogy without him revealed what I felt was actually true: The Trilogy doesn't change with or without Garrus.
ME3 without Garrus runs as normal. You go to Menae, get Victus, Victus and Wrex negotiate the cure for the genophage, Adrian Victus still crashes, and then he sacrifices himself for the bomb to be diffused.
The rest of the game goes on as normal as well, you can do the coup to reunite with Ashley and Kaidan, the Geth vs Quarian conflict to recruit Tali, every side quest, Thessia, sanctuary, and Cronos station.
I wasn't even reminded Garrus was gone until Tali went to the main battery when she and Garrus are scripted to kiss if they aren't romanced by Shepard. If Tali is gone, it's impossible to unite the Geth and Quarians. If Miranda is gone, Oriana does the leg work to stop their father , which gives her more agency. If Wrex is gone it makes the Krogan worse, Ashley and Kaidan are important players and one must be there for most of the trilogy. If Garrus is gone, nothing changes that much. You miss a couple of convos and that's it for the entire trilogy. I'm mad they did him so dirty and made him ultimately unimportant. He deserved better to just be a guy who agrees with you all the time and just being a follower.
**He deserved to be important beyond Commander Shepard.**