6th grade isn't bad at all. It is about the same level of reading as a TV sitcom. A person with a 6th grade reading level may be limited in regards to higher education, but reading won't be an issue in their day to day life or even most career paths. If you aren't challenging yourself by seeking good media and active reading, it is pretty likely that you will fall to around that level.

The best way to think about lemmy / kbin is that instead of a client / server model, where we have one facebook, one twitter, one reddit, we have one website that can view facebook / twitter / reddit all at the same time. They share, in this case, we can go to reddit and view facebook / twitter as well. So if facebook's /askreddit is better than twitter's /askreddit, we can view facebook's /askreddit on reddit and interact with facebook's /askreddit on reddit.

The great thing is that if server A has the best news content, server B has the best music content, and server C has the best porn content, we can be on server D and subscribe to all 3, and interact with all 3 seamlessly. And if we don't like the admin on server B, we can move the community to server E.

The hardest part is finding the best communities, since the are spread out everywhere, but once you find out about https://lemmyverse.net , it isn't so bad.