Healthy and unhealthy are composite binary terms that aren't useful. Specific, contextualized terms are more useful and allow for people to make better choices for the situation.

Maple syrup has considerable benefits as an alternative to HFCS. First, it's glycemic index is lower which results in a decrease in blood glucose levels. On top of that, it appears that it promotes insulation secretion.

Maple syrup is particularly rich in abscisic acid. This acid presents a strong defense against diabetes and metabolic syndrome because it promotes the excretion of insulin from pancreatic cells and boosts fat cells' sensitivity to insulin.

As a whole, in order to reduce ones propensity to diabetes, reduce sugar intake. Then, if further steps are needed and reduction is no longer an option, find appropriate substitutes. From the abstract:

This review presents detailed information about the nutritional, organoleptic, and pharmacological properties of maple syrup. Studies carried out on animal models and a limited number of human models emphasize the potential benefits of maple syrup as a substitute for refined sugars, indicating that it could contribute to improved metabolic health when used in moderation. However, further medical and nutritional health studies based on human health assessments are needed to better understand the mechanisms of action of the various components of maple syrup and its potential therapeutic properties to demonstrate a stronger justification for its consumption relative to refined sugars. In addition, we compare maple syrup and common sweeteners to provide a further critical perspective on the potential nutritional and health benefits of maple syrup.

And the final sentence:

More studies are needed to better understand how much maple syrup could be ingested, as part of a regular diet, to promote these pharmacological properties without triggering obesity or weight-related disorders.