Yuri's voice is limited. the biggest problem is that her voice sounds ALWAYS the same. when she does aegyo in the songs, it's super annoying, i prefer her voice in ballads. but even there, it sounds boring. look at Seohyun, her voice is similar to Yuri's, but Seohyun can bring some emotion, imo.
and can someone tell me why sometimes SM gives lines to Yuri that requires a high tone voice, that only Sunny, Sooyoung and to some extent, Jessica, can do? when Yuri does it, it looks like she's in pain
i will never understand

Maybe I think? but her voice can be annoying sometimes, her voice sounds like Tiffany

The problem with Yuri is she wasn't trained properly as a vocalist in her trainee days and still isn't receiving good training along with the other dancers because no one voice really has improved much in the dancing group. Her voice really isn't too much better or worse than any of the other dancers the only difference is that she doesn't have a lot of sound when she sings.

Dancing has gotten worse lets just be honest. She shows lots of uncertainty when she dances and has to look at other members all the time which mostly is when she starts to mess up. She is still the second best dancer, don't get it confused but she hasn't progressed. Her best dance is better than everyones except Hyoyeon.

She can always improve but the question is wither or not she is willing to.

^^to answer your question Yuri has a dark tone voice than Jessica and Sunny so that is the difference. Her voice even as high as it is isn't so high that it sounds annoying.

I highly doubt it. Her voice is only a little better than Yoona's and Hyoyeon's. And she should concentrate on improving her dancing first.

^what do you doubt?

I doubt that she could have a good voice one day after some self-improvement as the OP suggested.

I'm not sure I understood the question
If I think she has a good voice? Yes, not the best voice, but she HAS a good voice, that's why she is an k-idol
But I doubt she will ever be as good as the main/lead vocalists. Her recorded voice is nice, but her live voice is... worse.

^^anyone can improve their vocals so long as they aren't 30 years and above. Taemin improved his so its possible to just get a good vocal coach to help you.

i think her only problem is holding notes and reaching high notes.
to me, her voice has the most personality

totally can !!! her voice is actually awesome !