There are too few players compared to those years. Someone pointed out it's a community based game, which means less people in your community, less going on, less of a golden age.
Any LSRP golden age included a vast range of different factions that were extremely active. You still have latino gangs, black gangs, mobs, but there are no prison gangs, white gangs, barely any smaller cliques that fill up the world.
On top of that, most of us when we started were in our teens. The reason we won't return is because the ideal player base is a much younger age, with more time available. And that ideal player base is occupied with more up to date games. Which 15/16/17 year old is trying to play San Andreas Multiplayer?