In the first Mass Effect, the whole "hitting on your crew" thing is treated like it's actually a breach of regulation – even if you just go ahead and disregard that. However, by the time Mass Effect 3 rolls around, rules are thrown out the window and everyone's throwing themselves at Shepard. I guess the end of the universe will do that to you.
If you expected a bit better from your squad, we've got just the mod for you. The Optional Flirting Mod changes the way romance flags are triggered through conversation, meaning your crew won't get the wrong idea if you're just being friendly with them. This means that you can go through the story without having to rebuff everyone's attempts to get with Shep, and actually focus on that whole end of the universe thing.
"I've always found it frustrating that being friendly in ME3 tends to lead to fending off romantic interest from people you just want to be friends with, unless you race to lock in your love interest before spending quality time with anyone else", says the mod's creator, phoenixsoul13. "The former's annoying and the latter's a rather immersion breaking solution (not to mention not a solution for people who don't want to romance anyone)."
The mod makes all romances opt in, rather than opt out. Flirty dialogue is moved to the middle of the dialogue wheel so you don't accidentally lead one of the crew on, and going with the paragon friendly option won't trigger the romance.
Romance mods are nothing new for Mass Effect, but this is unique in the sense that it's making it easier to avoid them, rather than adding more. A recent romance mod added the ability to get with Ashley and Kaidan regardless of Shepard's gender, following the success of another which restored queer romance paths for Miranda and Jack in the second game, using unused dialogue.