I can definitely relate to this post and several of the other comments listed here.
Initially, most servers that I joined based on my interests are filled with much younger adults and sometimes teenagers. They are typically in a completely different point in their lives, so it's hard to relate or discuss common interests with them in general. Sometimes they use odd terminology that is common to their age such as: "Tspmo", "cheugy", "fanum tax", or "flexy mogging". To this day, I still don't know what these mean.
However, when I speak to most adults around my age, it's usually full of small talk or boring conversations that are one sided interests from them. Most adult servers are full of friend groups that have known each other for years, but it's the mainly those people discussing inside jokes or things not privy to newcomers. It's pretty much a glorified group chat that you are an audience of. I've been in servers where they gamify the friendship process with levels and ranks, but it's laughably disingenuous.
I tried hard to connect with people, but they rather discuss their one-sided interests without the opportunity to allow me to participate with them. These conversations are similar to the small talk that you would find around a water cooler at the office or at a bus stop. They weren't meaningful conversations, so I began to be more upfront about these things to people. Some people got upset while others were mature about it and very respectful.
My assumption is that since most of us are around 30 and older in the adult servers, we pretty much have multiple commitments (work/family/love/hobbies) and are more focused on those things and are "settled down" in a sense. I noticed in almost every conversation I had with other adults, there is always no time for new interests. It's kind of disappointing to hear.
One constant theme that I came across was high school level drama especially in the adult servers. Some adults cannot take genuine criticism and take things way too personally if you call someone out on their actions. What I found sad were servers where people would have to walk on eggshells for an administrator or owner of a server that legitimately seemed great. It was annoying how many invites I received in the past to join "X's" server because they did not like the admin's personal views/rules and other childish pettiness. Then they would act like they were all friends back on the original server. These people claimed to be friends for years!!! We are all people with different opinions, but It was jarring to see and it's what ended up causing me to unfriend and block those people. Honestly, that is the type of discourse that makes me not want to connect with people. It's genuinely made me consider leaving Discord and even places such as the forums in the past as I already have enough things to deal with in my personal life.
I wish people would communicate and clarify issues more openly. Over the course of the past few months, I have reduced my online friend group substantially as I am differentiating between acquaintances and friends. I'm planning to change it up more soon. Just because you have 50+ friends on a platform does not mean that they are your friends.
I rather have more personalized conversations with a small group of people that truly enjoy my company than be part of a large group that puts on a facade for one another.