I use nginx for that. I would like to see more software that provides the option to listen to unix sockets. Most still won't work with unix sockets. Some prometheus exporters at least support systemd socket units.
So for example if CUPS or Syncthing listened on a UNIX socket you can use NGINX to expose this over TCP, but now you are back at the original problem of any local process can access this service and you need to worry about port conflicts. You can work around this by adding access control but this doesn't elegantly solve the core problem.
So it is valuable to have a client (like Firefox) that can directly access the socket. This way you get native UNIX permissions and a whole filesystem namespace to prevent conflicts.
I use it to run a number of services under systemd, and haven’t had any issues.
Actualy namespacing syncthing per user might be enough for every user at same system to run syncthing at tcp/8080 or whatever.
I use it for the usecase you describe.