Today I am wrestling with the conundrum of how much is too much when it comes to system bloat. DnD is the best game example though this crosses genres very nicely. In every version of DnD from ADnD to Pathfinder there was an incredible amount of additional material put out for the game that added in spells, classes, weapons, feats, and other options that drastically increased the power level with time. For a new player these things eventually became overwhelming and the simple act of picking one feat at first level was impossible to do in an informed fashion. On the other hand the hardcore players seem to love having endless permutations of options to peruse to make bizarre (and usually overpowered) characters.
System bloat in other formats is usually a lot more benign. For example, in MMOs there is generally a constant stream of expansions and updates that add content and options. While the enormity of the system can still be a big challenge for new players at least the new content often obsoletes the old and new players can ignore much of what has gone before. Magic: The Gathering is similar to an MMO in this sense because maintaining a comprehensive collection continues to get harder and harder but the great majority of cards will someday become totally irrelevant. Still though a new player these days who wants to play Magic competitively will have a brutal time getting caught up with the veterans because there are so many expansions.
It is clear that adding content is mandatory to generate a large revenue stream but I don't think all of this churn is actually good for the games themselves. Certainly in a subscription model MMO churn is necessary because otherwise they could not maintain the revenue stream necessary to keep the servers on. In a tabletop game the rules are very different though. The publisher obviously wants lots of money and that requires new expansions but the game itself can be perfectly fine without them. Whether the expansion in question is Gods and Kings for CiV or Cities and Knights for Settlers of Catan the usual effect is to increase the complexity without really improving the game experience.
While having no expansions seems fine for the game itself it does appear that it makes for a small community. If you look at the most popular games and franchises out there it becomes clear that people really want to be doing the same thing as yesterday but bigger and shinier and are happy to shell out for that. Games that never expand or change do develop loyal followings but those followings are very small. The lesson I take away from this is that you don't need constant expansions and the problems that those generate to make a good game but if you want to make a lot of money or if you want a huge following you simply must produce a constant stream of product to take people's money. If you don't take their money somebody else will and they will go play the game they just bought.