Yes, microneedling is great to use on the neck to help with fine lines and loose skin. Unfortunately the neck area has very thin skin, which means it's more vulnerable to premature aging from sun damage and other factors. Another cause for the skin on your neck aging is "tech neck," which is caused by our obsessive use of technology (phones, laptops, tablets). Have a read of our article on tech neck here.
As the skin on the neck and décolletage is very delicate, you may like to use a lower needle gauge on this area, and you may also like to use a numbing cream if your skin is sensitive, or if you are new to microneedling. You can read more about needle depth here.