will he always take me for granted?

I'm dating a guy with ADHD and since we don't live together and aren't married, a lot of common problems don't affect us. But I do feel taken for granted. I feel like I had his interest in the beginning, and then I lost it, and now I only get it back when he hasn't seen me in a couple weeks and misses me. So when I don't have his interest, I'm low on his list. He agonizes over canceling plans with people who honestly probably don't care, but when he cancels romantic plans with me at the last minute he doesn't even feel the need to say he's sorry. I ask him to reschedule and he says he will but never does, and obviously there are no romantic gestures just for the heck of it. He fills our time together with work or TV, like I'm too boring by myself. He only compliments me on how I look or how our sex was. I'm confident that he's not just using me for sex, but sex gets his attention, and I don't think I do, anymore.

Some friends tell me I should tell him that he risks losing me if he doesn't put some effort into our relationship. But even if I didn't think ultimatums are a bad idea, even if it worked, it would be temporary. He'd attend to me while he was worried about me leaving, and then he'd start worrying about work again and we'd be back here. Thinking that through made me realize that it looks to me like this is just how it's going to be with him. Is that true? Is it the natural state of an ADHD partner to bored with you in between shake-ups that grab their attention? What does it take for him to care about me every day?