Depends on if you want innovation or stability. For innovation, people building fiefdoms over decades of political maneuvering is terribly destructive to change.
Very few industries require constant learning for the business to compete so a highly tenured employee likely hasn’t learned anything new beyond minute process changes for 10+ years. Once people are ossified into a role like that, they will do anything and everything to shut down anything that has a whiff of threatening their current role.
That is actually not my experience. I worked at a scientific institute on space cameras, and since projects easily last 10 years from design to launch, we have a lot of older people.
Some were resisting change. Some were embracing it. All in all, I had a great time and gained a lot of respect. I love working in teams with all ages.
Your sentence "once people are ossified..." feels like a generalization to me.
Very few industries require constant learning for the business to compete so a highly tenured employee likely hasn’t learned anything new beyond minute process changes for 10+ years. Once people are ossified into a role like that, they will do anything and everything to shut down anything that has a whiff of threatening their current role.