At my museum (Natural History Museum of Los Angeles), we have a large community science engagement platform. I am not directly involved with their work because it is all biology related, but they are quite successful at what they do.
Here is a link.
Also, the marine biodiversity center at NHMLA is quite active.
Both the groups mentioned above have many people (staff/volunteers) to make the programs successful. It's a lot of work. In my mineral sciences department, it's pretty much just my collections manager and me.
I agree with you, the infrastructure for community engagement is severely lacking for most people, but I don't what I would do to improve the situation. Social media platforms definitely help (which are the only tools I use), but it seems less than ideal to me. Things like iNaturalist do help, so maybe we more of that kind of community?
If you do find some nice resources/tools, then please do share :)