if she's so good at "becoming" other people... why doesn't that translate to acting?

this is something i've never understood.

if she's supposedly so good at adopting other people's mannerisms, aesthetics, personalities, etc. to the point where people didn't even realize what she was doing until years later...why can't she put that same energy into acting?

like, if she can study someone so closely that she ends up talking like them, dressing like them, carrying herself like them and people buy it for a while...why does she always end up feeling like herself in every role?? wouldn't acting almost be easier for someone who's supposedly that good at slipping into different personas? instead it feels like she just brings her current personality into every character she plays.

idk, maybe i'm missing something, but it's always seemed like a weird disconnect to me.