The game is populated. Problem is it's overpopulated.
Aden/Essence does not handle high pop very well because there is only 1 zone per level range. The complaint can be seen everywhere and it is an issue of game design. If it is too populated the game lags during events like Balok. TOI is prone to lag because it is such a big zone. The problem is exacerbated with a high client limit like 10 on NA. There aren't thousands of players. It's 100 x10.
The game will always be dominated by one clan on a server because it is the natural result of the game being p2w. Only so many "whales" willing to spend $10,000+ to be competitive in pvp. "Active" is relative. Vast majority afks with as many boxes they can afford. Hardly any active clans doing things like clan raids besides the top one. Vast majority of clans listed in clan entry are alt clans of the same people. The only real benefit of a populated server is economy and pvp if you are into it and can afford to do it.
Vanguard patch brought some updates to archers and mages, but most likely isn't enough to change the meta of dk/titan. It's pointless to consider pvp if you aren't willing to spend $10,000+ anyways and even that would still get you one shot.
There are no shortcuts to leveling in this game ever. The grind is the game. Maybe some xp boost events. 81 isn't much anyways. The "Hero's Starter Kit" was added later and will get you 81 in a week as it contains a bunch of red lanterns. Average player is looking at 1 year to 90 easily. It took over 1 year to get 91 to 92 on RU server. If you do not understand how L2 works, the game is probably not for you at all.
Then there is PK....
People are still here, but some came from EU Essence which has been open 2+ years now. PK was the reason many quit. Same one clan domination and pking everyone else. EU is in turn "dead" now. Some EU refugees currently playing on NA most likely like the higher client as EU is officially only dualboxing.
Essence is actually quite popular. This is not the problem at all. Problem is there being multiple regions and servers. "Illegal" servers are thriving and there are thousands. RU has their own server that is populated with good reviews. They are also cheaper.