Incompetent Mid-Aged Male Coworker

The title of this may be harsh and I know I'm preaching to the choir, but how is it that middle aged men continue to be put in senior positions they are not qualified for? I'm in year ten of my career and it's so disheartening and frustrating to see in every role that I've held. I've especially had it hard lately as I feel like we've been building a case around him for at least a year and a half. I understand it's a sensitive subject and takes a while to loop in HR and what not, but how much longer do I wait? I've voiced my concerns to my superiors who also recognize the poor behavior. Two people on his team have already left in the past couple years. Any thoughts on how to continue bringing this to attention and escalating? This person is director-level but is incapable for putting forth anything strategic or thoughtful. I try not to get frustrated by the situation but each day, it's tough, especially in our current environment. Any advice is greatly appreciated.