It always depends on what you want to use forum software for, how user-friendly your forum is, and, most importantly, your niche. The way you structure your forum with categories and topics also plays a big role. On top of that, you need to offer something valuable to your readers: interesting content that you create yourself.
Then there’s the reality of the SEO game and the huge amount of competition from other websites and forums. That’s why it’s important to focus on long-term white-hat on-page optimization, such as building high-quality backlinks. It’s a lot of work, but it really pays off in the long run.
Most successful forums have one thing in common: they hit the right niche. So, find your niche, publish plenty of blog articles and forum posts, and work on getting them to rank. Over time, your forum will start to grow.