I am the "Dan" in my group of friends. Let me share my own personal experience and thought process with you. I'm not saying that this is exactly what Dan is going through, but hopefully it will just help you understand that maybe his behavior isn't intentionally to hurt you or because he doesn't care about you, maybe there are other issues that you're just unaware about.

My friends from high school always try to contact me, and they are always the ones to initiate get togethers. Whenever we see each other, we have the best time and act like no time has passed. I'm sure they get frustrated like why I'm not as responsive or quick to respond as others, and why I rarely initiate anything. I understand from their perspective that I may be a "shitty friend" and my behavior may be perceived as lack of trying, but what they don't know is that I have social anxiety and being in public. I am only ok if I'm out with my family or close close group of friends. They always wondered why in high school I would pass on dinner and movie nights on Fridays or Saturdays, but so many times I actually spent the time getting ready and couldn't get myself to leave out the door. Even though these are my closest and best friends in the world, they don't know my struggle because I haven't shared it because I'm ashamed of it and have been working on it slowly through the years. It's not like I'm an awkward person in life with no friends either. I was the captain of the cheerleading squad in high school, but it was all an act because inside I am deeply insecure and deeply scarred by certain events in my life (taunting, bullying, racism from strangers in public, etc.).

As for why I rarely initiate hangouts with my friends, it's like even though they are my closest friends, I still have a fear of rejection from them. I know it sounds weird, but again I think the way certain events have affected me from my past have definitely made me an insecure, anxious person who overthinks everything.

I'm not saying your friend has my same experiences at all. I just wanted to share my story so you know that just because he acts the way he does does not mean that there's any malice or carelessness behind his actions as most people might assume.