While a steady stream of content updates are constantly adding new gameplay mechanics to GTA Online, there is a trend in Rockstar's DLC style that would make calling these "add-ons" more prudent instead. Namely, once something gets added to GTA Online, it is rarely changed — or "updated" really.
Both Cunning Stunts and Further Adventures in Finance and Felony have added all new layers to gameplay in order to keep the game fresh and the players engaged. Cunning Stunts added all new Stunt Races and Premium Races with an overhaul of the Content Creator on the way. Finance and Felony added the whole new CEO system, including buying and selling missions wherein you need to transport precious cargo to various locations on the map.
However, in spite of these updates, some of the core mechanics of GTA Online haven't been touched since initial release in 2013. While the game remains one of the most polished, content-rich, entertaining and popular multiplayer experiences in the world, there is always some room for improvement.

While the relatively recent Freemode Events update did mix things up for the random faffing about aspect of the game, it didn't revisit the basic mechanics. Finance and Felony accentuated the issue with Hydra griefers, sparking a hate in the community burning almost as hot as the spite felt towards the hackers (though that particular issue has been solved).
Some players have proposed a very simple change that would make the trolling of the griefers much more difficult, would make stealth meaningful, would freshen up PvP and lend random firefights a new sense of freshness — remove player blips from the map.