I suppose that depends on the meat you use and how else it's prepared.

Use a high fat ground beef and bread crumbs that'll soak up that fat, and I'm sure many would consider that unhealthy.

Use lean meat and something else as filler (oatmeal is common when trying to fill out meat) and it would be less unhealthy, but far more prone to error, resulting in perhaps a tasteless brick.

Never read on meatloaf, but I'm sure a publication would go the "easier but fattier" route.

I wouldn't call it unhealthy, unless you're of the mindset that red meat is inherently unhealthy. It does retain most of the fat from the ground beef which would cook out of normal burgers or hamburger steak. But it's also more filling than either of those due the fat and the inclusion of bread crumbs or oatmeal as filler.

I suspect as with many things the quantity plays a factor.