I quit learning violin as a kid because my left arm simply would *not* do vibrato, and it was required for grade 6. My wrist/elbow just wouldn't do it, and after 6 months+ of hassle and getting nowhere, all the fun had gone out of playing and I quit.
Now I fake it with a rock-guitar-style vibrato instead, moving my finger side-to-side instead of moving my hand along the fingerboard from the elbow or wrist. It doesn't sound the same but it's good enough for folk, and it's something that I *can* do.