Creating an Interesting Main Character

I don't know if it's because I write in first person, but creating interesting main characters is my downfall. When I think back to every novel/novella I've published, almost every one of my main characters is interchangeable with the others. Whispers in the Dark (originally titled, Radio Crazy) featured my most distinguishable main character, but I was told she was unlikable, so I changed her personality in the rewrite. I, the only person apparently, actually liked her original incarnation, because at least she didn't fade into the woodwork. She was cynical and impatient, and didn't suffer fools. But I surrendered to a biting critique and softened her. She still tended to fly off the handle, but she'd immediately apologize. I don't think that made the character better, but many readers don't seem to catch onto the psychological effects of almost being murdered, and thus I turned her into a passive nothing.

Aside from the original Whispers in the Dark character, though, all my characters are reactors. Sure, they occasionally make things happen, but they act more as the narrator of the story. I can't seem to overcome that. 

I did a bit of reading on the subject, but have yet to find any usable suggestions. "Personality contradictions" seems to be a big one, but using Jane Austen as an example is really broad. Lizzy Bennet liked to read, but she also liked to dance. Well, who doesn't? I can't have my MC's just reading and dancing all the time. 

"Experts" also posit that the character needs to have a motivation and a goal. Honestly, the majority of my MC's have no goal, or if they do, they're unaware of what it is. Take, for example, Leah in my current manuscript. She doesn't even know if she wants a singing career or not. Sometimes she does; sometimes she doesn't. She was offered a recording contract out of the blue and was all set to decline the offer, when suddenly she accepted it. Why? Because "something" happened to her ~ not that she actually forced the decision. And therein lies my perpetual problem. Things happen to my main characters and they react to those things.

Oh, they occasionally drive circumstances, but when those things happen, they seem to arrive out of nowhere, personality-wise. Leah spends most of the novel basically following either directions or outside influences, so when she suddenly asserts herself, it's disorienting. I can think of three direct actions Leah has taken so far: she quit her original band, she lied to get a hotel room, and she fired two of her employees. I don't think readers can connect with my main characters, because I don't give them anything to latch onto. 

The whole process is a needle I can't seem to thread. On the one hand, it's not a story unless events happen, but on the other, I'm so intent on advancing the storyline that all I can manage to do is write the MC's internal reactions to those things. Can an author develop a main character's personality simply by revealing her inner thoughts? Doubtful. 

Most likely, prolific authors don't create a certain personality type for one novel and a wildly different one for the next. We all lean on what feels natural. I'm probably overthinking it. Who but me is going to look at, for example, Shadow Song and Bad Blood, and say, Why, those two characters are the same! 

Aside from digesting useless articles on the topic, creating an interesting, unique character is just something I'll need to master on my own. 

I'll add that to the long list of elements I've yet to master.