What should I do with my once active community

Hello fellow IH, this is my first post here and this topic isn't the reason I ended up here. However looking at the helpful and active community I thought I will surely get some thought provoking ideas.

So I run a tech forum, techenclave.com, which was established in 2005. At its peak it had over 300K unique visitors per month. It had always had google Adsense as the primary revenue source.

Past several years it has been going south as I have not made any efforts to take it in any other direction. It's at about 10% in terms of traffic of what it used to be. Mostly the loyal members have stuck by but still 90% of the traffic is through google.

Now I am thinking I should not let something that took a lot of effort to build just fade away like this. The forum community however is not what it used to be a decade back. So the things that brought it here probably won't take it forward (I almost quoted Marshal Goldsmith there :D).

So with that backdrop, I ask you, how do you suggest I take this forward and make something worthwhile out of it?

TIA