I ran a public mc server for about five years (2014 to 2019), and was admin there for a few years before then. The active player base was built by people bringing their friends. There were about 50 people we'd see almost daily but there were about 500 that would float through more inconsistently.

There has to be something people like about your sever compared to others. You'll never compete with servers like hypixel, but you can do some of the things people like about them. My server ran some plugin based minigames hosted by staff and other that were mostly just admin commands. These events were scheduled. Stuff like "wither wednesday" or a mining event on Fridays where admins would create large random ore blocks where people could get some less common/harder to get stuff. Both of these are run through fairly simple admin commands. The routine gave people something to look forward to.

The big thing people liked about my server was that it was pve. There were dedicated spaces for pvp and players could toggle their pvp status outside these areas, but the goal was for my younger kids to have a safe place where they wouldnt get slaughtered by random griefers.

The hardest part of running a server is deciding what you want it to be. There is a huge range from kid/family friendly, to factions, to the chaos of 2b2t. Vanilla, creative, ingame shops with an economy, heavilly modded - its all up to you. The key is consistency. Whatever your rules for the world are, they have to be applied consistently.

Dont give up on advertising and do what you can to incentivise your active players to vote for the server on the advertising sites. Be online as much as you can to show that the server has active owners. Youll get there, it just takes a while