As someone similar in age I have experienced some of what you write about.
A couple of things. First I know I am one of the only ones in my age group that regularly attends Al-anon. Give it some time though....I have still made some great friends through the program...and others come in that have been closer to me in age in teh last 18 months. Also I have at times attended larger "group" meetings and have met people closer to me in age.
Secondly I don't know if this is part of it or not but it is not alcohol related. My friendships have started to change in the last 5-7 years in addition to the changes with a loved one in my life with alcohol because of many of them having young children and their social life changing. It is not that we are not close....there is just only so much energy to go around.
Finally I have found when I started being honest with what I was experiencing I got a lot of support, and sometimes from unexpected sources. Some relationships were strained (and some continue to be in transition for me), but the relationships I do have now are more supportive, healthy and appropriate. They work for me! I have not always had that as often I set up relationships about helping someone else.
Good luck. Being in a hard spot can be so hard and feel so isolating.