GTA V single player was great in most cases, even if the customization was lacking in every way.
The online launch, on the other hand, was so bug filled that they decided to up the ante by patching out the fun week by week. 700 missions? 500? try about 24 with half of those paying absolute sh*t. So you want to get cash in the competitive modes with the level 200 boosters? how about the crash fest that is public racing? Slipstreaming is a great idea to give people a chance at fishtailing you out of first place.
There is very little to do that is reliably fun, and the mission variety is insanely lacking.
Most importantly: why wasn't there a beta? too worried about their metacritic ratings to make a solid online experience before launch?
To summarize: the single player is a leap forward in terms of the character switching, but the lack of customization and sparse cash flow reduce the fun. The online is simply undercooked and we should have had an open beta.