It might be worth taking the time to carefully examine your hand position and physical technique. Simply practicing more won't help much if your technique is fundamentally flawed. A few specific things you might want to consider:I want to record some stuff to show as an example, but basically...Inconsistent volumes or inconsistencies in how I strike the string with my finger. This can be most notable when playing quick 16th notes.
1. If you always anchor your thumb on a pickup, consider learning to use a "floating thumb" or "moveable anchor." A problem with planting your thumb in one place is that you have to change the position and shape of your hand to reach different strings, and your angle of attack can differ from string to string. An advantage of these other methods (in addition to muting) is that your hand shape and plucking angle stay exactly the same no matter which string you're plucking.
2. Is the wrist of your plucking hand severely bent? A lotta folks tend to rest their forearm on the top of the bass body, almost parallel to the ground, and bend their wrists at a 90-degree angle (or more) to reach down to the strings. The wrist-bend saps a lot of the strength and agility from the plucking fingers -- not to mention increasing the risk of injury.
3. Relatedly, having a lot of tension in your plucking hand will similarly sap strength and agility; it needs to be relaxed and tension-free. One of the reasons I personally like the "floating thumb" method is that my hand feels much more relaxed than when I anchor my thumb on a pickup.
4. Are you plucking harder than you need to? Turning up the amp and playing with a gentle touch is another way to keep your hand relaxed and avoid wasting energy. In my own case switching to the "floating thumb" solved this problem at the same time: I find it much easier to pluck softly than when I anchor my thumb.