I also find it a little disappointing, the reluctance of mod use in some sims online.
For a couple of years, I have been running a daily server with new, up to date, interesting and stable mod content (mostly just tracks with official and DLC cars)
AC tracks like Thompson, Bridgehampton, Fuji68, Donnington, Road Atlanta, Road America, Riverside, VIR. All of these tracks are incredibly well done, with great potential for vintage, or class lapping and/racing.
If I get more than 3 or 4 drivers a night, it is unusual.
We always have a great time, and the mood is relaxed and mature.
In the case of AC, I think many users look at the list of servers, and see an entry that has some of it's content in the "red" text, or they have the "don't show servers with missing content" button enabled, and just move on.
If there was a comment box for each server on the AC server listing allowing for more info such as "download this new amazing track from Race Department" or just more info about the server, it would increase the online mod adoption.
Trying to show a quasi link in the name of your server, is just confusing.
Currently most of the online mods in AC are restricted to Drift servers which is great, but I would like to see more participation on some of the other mod servers.