You should find something more interesting than games on Mineplex or any other big soulless server. There's 5000 other videos of the same game being played and new people have no reason to decide to watch yours among all others.
You could go the mod route if you wanted to. Modding is easy to do now because there's tons of modpacks that do all the work for you. Even then, I'd stay away from things like the big popular modpacks such as FTB, because those are also oversaturated. If you're up for a challenge, try out Terrafirmacraft. As far as vanilla servers go, I can't say I know any good, obscure servers anymore. They're out there if you look hard enough, but you'd probably find that getting good footage on them is hard owing to the lack of players (just look at Conwy- most small servers look like it now) If you're willing to do singleplayer (or local multiplayer) videos, try out some adventure maps. There's enough out there that you'll find a lot that aren't overused.