Meringues shouldn't be gooey inside when baked properly. But it's normal for the centre to be soft and marshmallow-like rather than dry. Baked meringues will lift off the tray easily with intact bottoms and the outside will look dry. Some moisture inside is ok, but stickiness means it's underbaked. The inside crumb should never be syrupy or translucent when you cut one open. The texture might be pillowy and soft but not gooey. A bit of moisture is fine, but excessive stickiness means the meringue needed more oven time to fully dry out inside without the exterior browning too much.