There's a spot in the opening of ME3 (Escaping Vancouver) where Anderson cheerfully chides Shepard, [Forgive the paraphrase] “Come on, it can’t be that long since you’ve handled a weapon!” In my mind, my Shepard replies, "Been awhile since I handled one this crappy,”

More than likely it was an attention to a detail that got cut due to time restrictions. They can give NPC's "better guns" because they program those characters to have them. On the other hand, Shepard has a wide array of options and being able to code for every possibility became impossible. So, design the basics and hope the player squints! :)

@Shenachie slander against my beloved Predator 😭

@Zjay47

Tut, tut, now ... everybody has their preferred toys.

I have learned the value of keeping the Predator handy until the killer-bot is dispatched on Mars before I go get my Carnifex/Black Widow. 😎

I love the Carnifex, but something about it feels off in ME3, maybe it's the faster paced combat, it still looks cooler and sounds better, the Predator looks like a plastic gun unfortunely and sounds like crap, but i can't resist that fire rate, especially if i have Incendiary ammo

Don forget the about the Predator’s high ammo capacity which with ammo mods and powers combined with the fire rate makes it really dangerous regardless of of its low dmg output since you can just fire and reload without worry you Will run out soon.

A good Soldier build focused on power combos can kill a brute in seconds with it by setting up fire detonations

Infiltrator can go for pistol appearance since main damage comes from the Black Widow. The Carnifex is mostly used to shoot doors off fuse-boxes. Experience instructed about the Predator and the Mars killer-bot, and that the Citadel elevator-brakes respond better to a good SMG. Survive (or Reload) and learn! :)

It really depends on your build and play style, for Infiltrator the Predator probably wouldn't be useful, but there might some builds that would make good use of it, i never played Infiltrator in ME3 so i wouldn't know, compared to SMGs the only ones that really match or surpass the Predator when it comes to fire rate are hard to control, but still good options so it's up to you what you prefer, i like both.

L mass effect is the most perfect game ever

There's actually mods that fix that and make it whatever weapons you have equipped in the cutscenes.