You just described capitalism as it exists today. Even if you did away with immigration, your problem has barely seen any solution at all.

If your fear is being replaced by someone who is ready to work for less. There are enough kids who will do anything for a job, including taking a good pay cut. To replace you.

The real issue you must be worried about being relevant to the work you are doing. Being productive, resourceful and keeping your skills up to date. And yes never putting yourself in a situation where you think some particular work is beneath your station.