You know the easiest way to make a horse be hard to catch? To only go to him when you want something. And not spending enough undemanding time with them. And
not making the time you spend with them full of softness and quality.
So, here's what I would do. As you walk towards him pay attention to his ears especially. Don't walk in a straight line, mosey and kind of go back and forth along the path like you are drunk lol. If you ever watch horses come to say, the water tank, they never go in a straight line. They swirve, so you need to do the same. Now, you want both ears full forward on you. If at any time he peels one away STOP. That's him telling you you've hit his threshold and he isn't comfortable with you coming closer. Relax your body and wait. If he puts both ears full forward again you can proceed. But, if you are waiting and waiting and waiting and nothing is happening turn your belly button away from him. When you are facing square on at a horse that is a lot of pressure. When you get to him, scratch an itchy, give him a treat and then LEAVE. Don't halter him. This will blow his mind and he will become more curious.
Do this several times a day. And when you actually halter him don't have a work session, just take him out to eat grass. I would keep this up for a week, maybe less depending on how he reacts, maybe more. You'll be amazed at how this changes his perception of you.