Fine motor skill means the fingers doing small, precise, separated work, and almost none of it starts in the fingers. It starts at the shoulder and the trunk. A hand can only be accurate if the arm behind it is steady, and the arm is only steady if the middle of the body is. Then the hand has to learn to split its jobs: thumb, index and middle finger do the moving while the last two fingers hold the base still. Some kids pick that up from climbing and carrying and messing about. Some kids have to be taught it.
There is a second half, and it is feeling. To do a button without looking, your kid has to sense how hard to squeeze and where the fingers are. When that feedback is fuzzy, the hand grips too tight, tires early and quits, which is why “try harder” and “practice more” so rarely change anything. A comprehensive initial evaluation sorts out which layer is short, the strength, the stability, the finger separation, or the feel, and the plan starts at that layer instead of the worksheet.