This is not an uncommon appearance for a laceleaf Japanese maple for this time of year. An accumulation of minor leaf infections and stress from summer heat and drought can all contribute to leaf loss before autumn. Several leaf infections, like powdery mildew and anthracnose, cause similar-looking symptoms, although none needs to be treated with fungicide (a spray would not cure existing infections anyway).

Although bare twigs right now are probably not dead unless they have been bare since spring, if any branches or twigs did die back, Botryosphaeria canker may be the culprit, as it's an opportunistic fungus that takes advantage of stressed plants, especially due to drought. (Maryland has been experiencing a drought for much of the past two years, and unless you've been watering periodically, plants are likely stressed.) If any branches or twigs do not leaf-out along with the rest of the tree by mid- or late spring next year, you can trim them off as they are likely dead or too weak to recover. It would not be unusual or greatly concerning for a tree this mature and dense with branches to have some accumulation of dieback scattered among its twigs, so that alone wouldn't be a great cause for alarm.

We don't see a need to replace the plant, but you can wait to see how it fares next spring, which would be a more fair assessment of its overall health compared to late summer and autumn leaf disheveling and shedding.

Miri