Hey! People usually start advertising since the moment they start developing, that's why writing devlogs and releasing demos is so important to promote your game before launch.
I've seen teams promote their games on other platforms such as Bluesky or X, and Discord servers are a great way to get an audience as well. I'm sorry to hear that your game is not getting traction, but unfortunately players won't be able to play it if they don't know about it.
As for hiring advertisers, a handful of developers do that, but it's not a must. What's important is to get your game out there and players will appear naturally.
This is a great space to self-promote, though! Asking for feedback on your game, even if it's finished, may help you improve new builds and use that knowledge to implement it on new games. I hope you can get more players to try it!