A lot of Blockland Discord servers are private/sekrit klubs so you need to know somebody in them to get an invite and even then they may have some weird invite process like holding a survey or asking other members if they're okay with inviting you.
Seriously, there's a lot of elitism here for such a small game community.
Mr. Lol's BL servers discord, the one of mine I just linked, Blockland Content Creators, and Kreon's server discord would be examples of public discords.
The rest are cliques that can outright hate each other and you won't get in unless they want you.