It might help to know what problem you want to solve. One possible reason for wanting fewer topics is that it can be overwhelming to new users. In that case, you might try using a variant of the Category page as the default. To do that, adjust the order of the top menu setting so that “categories” are up top:
Then you can experiment with the desktop category page style setting. “Categories and Latest Topics” works pretty well, in my experience.
The advantage for new users is that the list of categories helps people get an idea of what’s on topic and the latest topic section shows a sample of what’s currently being discussed.