I don't think so. Modding keeps pc GAMES going and not SIM's.
For example in case of GTA its fine(btw iam talking about car mods and stuff like that, not the multiplayer hacks and other stuff...)
In Case of SIM's ? No not really. A SIM "will be going" if the community is good.
For example i was in F1 CH 99-02 from the beginning and it had a few great mods but the community was not so strong, i still played it for years because we were driving with friends in a league but the other online lobbies were empty most of the time.
Another example: rFactor, If iam not wrong, rFactor is a Racing game with the most mods. I think there is a mod for everything in rFactor even a Horse mod
iam not joking.
But whats going on with rFactor now ? i looked up the servers last week and all were empty , only 2 of them were with players and that were closed lobbies with password.
rFactor 2 ? Its a good game and it has good mods too but its dead, maybe "dead" is a bit to harsh but most of the rFactor drivers are actually driving Assetto Corsa or even Game Stock Car (which is a game based on rFactor).
The Community keeps the SIm going.
Another example: I started with Assetto Corsa 3-4 weeks ago.
The game itself is quite good, but the community , OMG just horrible.
In these 3-4 weeks i already know EVERY good driver in Assetto Corsa's Multiplayer. Less than 10 who are actually playing it. We know each other and if we are online we have great races, but whats up with the other drivers ?
Crashing, driving unrespectful, rules ? what are rules ? coming out of the pit and staying in front of the guy who is actually on a fast lap - dont care.... stuff like that.
So lets immagine Assetto Corsa with 1000 mods, would i play it ? The car itself doesnt matter if you dont have people which you can race with.
The best example: Gran Turismo 5. I played GT 5 nearly every day and i can remmember the first day where i saw a modded car. It was quite fun and the guy who was driving the modded car was quite nice and he sent me one too...
First 1-2 days were fun but then ? I already had a bad feeling because i knew it will destroy the core of this game . RACING. And after that i wasnt really playing GT 5 anymore, i joined a few server just to look if there are new 4329074529045724756235ß6 PS cars and after a week i stoped playing it. I had such great races with Gt 5, bumper to bumper every lap every corner without hiting the car in front of you , just epic races . And all of that was dead.
People who were messing around in GT 5 ( these guys who are crashing all the time) they loved these mods, and the real Sim races left GT and played if offline or played something else...
Thats how i think in case of moding and Sim Racing.
But you are absolutly right if it comes to games like GTA ; )
ps: I am not only talking about the 345235245 HP cars, stuff like : taking a Stock Clio and increasing the Grip level a bit so that your Clio is stock but you have an advantage over your oppenents in online races... It just destroyed everything.