Longtime juggler here.
Outside of more complicated tricks like the claw and other specialized patterns, the most common juggling patterns (such as the cascade [1]) don’t rely as much on pure handeye coordination as they do on maintaining a consistent, even toss. The key is throwing each ball so it rises and falls in a predictable arc, so it lands approximately in the same spot where your other hand is waiting to catch it.
When I teach complete beginners, I actually start with a set of special handkerchiefs. They fall more slowly than balls, which gives learners more time to react and makes it much easier to see and follow the path of each object through the air.