He's not in the position to say "my way or the highway". He's in a highly competitive field that moves quickly, and he wants to play at the top level. He needs to adjust or he will miss out. He's definitely not in control. He still has ambitions to play at the top so being able to retire is irrelevant, if he retires now he'd look a mug and be disappointed with his career I bet.
De Gea also didn't get what he wanted, he had to settle because none of the clubs he wanted would pay him what he wanted or they didn't guarantee him as a long-term starter. Being a footballer is not like working a normal job, they do not have the same power as they're replaceable, they lose value the more they don't play, and their careers are short.
Robiot is good, but he's not so good that teams are desperate for him.