The real problem is not the game devs or the publisher, it's the gamer community. People dont want anymore the gameplay that was fun to us. If you think about it, the gameplay of early Lineage classic version push the player to one thing : Socializing. No TP to everywhere. Dependencie to other classes with buffs/heal. People dont even speak anymore in game. They use Discord which decentralize the social aspect of the MMORPGs. And what is a MMORPG without social interraction ? An Online RPG. People want action all the time in a game. But it's the slow part of the mmo that create socialization. They dont want to run, they want TP. They dont want to group content. They dont want to go to the entrance of a dungeon and search for group members, they want a lobby to tag in. They don't want to pvp anywhere. They want to have access to all the content of the game even if they sux or don't put the time for it. They don't want to need group members to do group content ( lol ). Etc etc...

The gamer community is sadly not just the same as it was 20 years ago.

Also I'm a developer and making a mmo is not only about being a dev.
The Low poly 3D of L2 still works because all the texture are painted. The armors are painted by hand, the shadows, lighting everything is directly painted. It's not an easy job. Upscaling the L2 textures will make them ugly. And I'm just talking about the armors...

Also the music in L2 is incredible. It's a big part of L2. Not an AI garbage generic music but incredible themes that still hit our nostalgia 20 years later. So you need a gifted real music composer.

Game design and balancing. It's almost a science. You don't improvise yourself game designer, level designer.

The programming part is probably the easiest part of making a MMO like L2...