Finding a good Minecraft server to join

Some people say it's best to stick to the most popular servers, as they usually have the most active communities and content, but others swear by smaller, niche servers for a more unique experience. I'm trying to decide what kind of server I should aim for in Minecraft these days. My friends and I have been playing on a private server for a while, but it's starting to feel a bit stagnant, and we want to explore broader communities. We're looking for a new adventure, possibly even something competitive. What are your criteria for what makes a server truly great and worth investing time into? I'm open to all suggestions and different types of gameplay.