I think Boost CS 1.6 can make sense in that situation, especially if you already have something worth bringing back. An old server with a recognizable style and a few returning players has an advantage over a completely empty new project because there is already a foundation for a community. The important part is getting enough visibility for new and former players to notice that the server is active again. You can look at https://unikov.net/ and see what promotion options are available. A dedicated CS 1.6 platform is more relevant than general advertising because the people discovering your server are already interested in the game. I wouldn’t expect a boost to rebuild the entire community instantly, but it can help create the activity needed to get regular matches going again. After that, keeping players interested with good administration and consistent gameplay becomes just as important as promotion.