You said you are "not intimate anymore" in your post above.
So - one of both of you is avoiding it, no?
He can kiss and he can have sex. He did early in your relationship - he chooses not to now, albeit the "choice" may be driven by his autism.
He really gets to call the shots, doesn't he? Do you want to expand on your comment that pressure is being thrown at you?
In my opinion, an anniversary isn't a big deal and especially if you're not married. But - you have both clearly made it a big deal before - OK, that's your thing.
If he wants a weekend with friends, I don't see any reason why it CAN'T be your anniversary weekend. I think it'd be childish to stamp your feet over that.
But it's perfectly acceptable to say - great, I'm looking forward to that - but I'd like us to do something romantic as a couple too. How about we do x on y date?
It's also perfectly reasonable to tell him that this made you feel - whatever you felt. It's childish to insist on a set date, it's not childish to talk about your feelings.
He can't/won't give you what most would consider to be a normal relationship. Just make sure that doesn't mean he doesn't get to call the shots on everything! Don't make autism an excuse for him not being romantic on your anniversary. Even if he doesn't feel that social norm, he knows full well that it exists, as evidenced by your previous years.
Remember that just because someone has autism, doesn't mean they're not also in the wrong!