In a musical in recitative it is. That's the whole point.
If the songs were the whole point, there wouldn't be any need for the recitative. It's true that the song can do heavy lifting in revealing character and evoking our emotion, but the dramatic interactions, in recitative or ordinary speech, are also character presenting.
We don't know what her problem with the other women at the factory is; we don't understand her secrecy; we don't see any effort to find another job so what we see is an immediate descent into prostitution; really, we don't even know how such a woman the dialogue says she is could abandon her child to the grotesque Thenardiers! Nobody is stupid enough to trust those gargoyles.
All these things are her character, but they don't add up. I read Les Miserables over forty years ago, so all I can go by is what's on screen. Maybe other people are using something else to fill in the gaps there.
Her performance isn't just "I Dreamed A Dream", anyway...
Absolutely true, and the failure of the rest is what diminishes the character to essentially one song...which isn't enough. (Incidentally, the problems with Fantine are in the script and the direction, not Hathaway. I can't see anything that Hathaway didn't at least try to turn into a genuinine human being.)
(I thought "Lovely Ladies" and "Come to Me" are almost on the same level, anyway)...
The vampire hooker chorus does a smashing job of asking the question of why this woman doesn't go steal Cosette and either steal or beg. The ghoulish delight in degradation that powers "Lovely Ladies" gave me another take on the sincerity of the refrain "Hear the people sing!" I thought the song and its staging were awful. I suppose if you liked it then it might have added to your appreciation of Fantine, but I'm sure not seeing it.
...and she does a superb job in mine and many others' opinion of conveying her character.
I still don't think she sang as well as a professional singer could have, and the performance would have been better. Nor do I think she successfully surmounted the script and staging problems. But it's quite true she managed to do a decent job of evoking pity, especially in the hair cutting scene I thought. But lots of actresses can evoke pity in such lurid scenes of degradation. It's a bad actress or writer who wrecks a death scene too. But...a prize winning performance better than every other supporting actress? Really? That's a stretch, even if it lese majeste to say so.