What? No it didn't. It didn't have online multiplayer at all (let alone customizable missions and a stock of several hundred pre-made ones), no bounty hunting or hunting, very few of the GTA V activities, or random encounters.
More to the point, San Andreas had to have so many missions because its narrative traveled across three cities, the countryside, and the desert. GTA V is restricted to one large city and one VERY large rural county. San Andreas needed enough missions to fill up each of the five unique areas to a decent degree, plus a return to Los Santos for the endgame missions.
It had equivalent stuff to most of this... ambulance, fire truck, police, pimping missions, street racing, off road racing, nascar racing, driving, pilot schools, hidden packages, chiliad challenge, in game video games, NRG challenge, customizable cars, fighting gyms etc. etc.
Point is SA had a similar amount of content AND more missions, just sayin'.