All connections appear good.
My first reaction is a poor connection in the high current circuit for the starter. Sometimes they can look good but have some corrosion between the connections. I would eliminate that possibility completely before I got into the expense of pulling, checking and maybe replacing the starter motor. Just to add to what JB said, yes the starter could need rebuilding or replacement if the connections all look good. Take a heavy screwdriver,and jump the high-current side of the solenoid.