I think a few others have hit it on the head--you may be getting bored or not finding satisfying RP because you've left not as much to be interactive about, and are too reliant on others to make things for you to do with your character, vs. being open to having them effect you.
Staff run plots often have a huge number of signups (as do sphere events). IME these may be exciting actiony things but very very rarely will they introduce you truly to others or get contacts outside your playgroup. There is a scene, but then a lot of people do not get together on their own afterwards (maybe in a job, but even then people tend to do that individually or in clusters). There also are not typically enough of them to constitute regular RP. This isn't a good or a bad thing, just seems to be par for the course for most places I have played at least in the last decade.
I find when people are way too focused on their own PC being a specific way and interacting in the world a specific way and/or wanting to surround themselves with others and events that go in such a direction as to support that, it rarely goes well--especially if you're not communicating a lot OOC (and even if you are). I think most people who MUSH fall into that a time or two so it's by no means some indication of not being good at things or whatever. But you do have to be careful of an attitude of "I have such an awesome PC, if only people would come and unwrap me and see!" creeping up on you--because a lot of people are used to that kind of interaction being very one sided, when the other person won't run things/won't focus on the other PC for a change, ect.
IME games are not made exciting or interesting by /your/ PC, but by what develops between them and others. I tend to make rather open ended PCs so I have ready excuse to explore without being too bound by "Oh, I can't do/explore that, because I've had 50 years of doing something else/in my background I /hate/ that, ect." Most of the PCs with elaborate backstory (which can be rewarding, but IMO primarily when you are creating that WITH someone else, not on your own for someone else to try to discover from scratch) that I've had have had a partner to play off of and a reason to be very very very interested in the world around them. (Spy, courtesan, political machinist, personality, ect.)
If you listen and yield the spotlight and pay attention to what other people RP with their characters, you'll often build goodwill. I can't tell you how many times people have been touched that I remembered something said in play and incorporated it into our next scene or in an offscreen moment (like a @mailed letter or gift, ect). I do that because I enjoy it. It is not super reciprocated, but when it is, I know that that person is a keeper for RP and someone that I'd like to involve more, beause it really does feel good when someone notices and is thinking about your PC as they're writing about theirs. And you can do that sort of thing regardless of backstory.
I think the most helpful thing to remember though is that your character is often not the prime reason why you do or don't enjoy a place. Your interactions with others, their relationships with others, and other things often affect how and if you settle and how well so much more than your character themselves.
So I think it's good to leave some open space. It is really good to have a concrete idea in your mind of what your PC is like, but I think realistically on a MUSH you should be willing to adapt a little if the environment is different than you anticipated or be willing to ditch your PC (there's nothing wrong with ditching something that's not working for you, and nothing wrong with trying alterations or giving it time--it's just a matter of how much you'd like to invest or are willing to be patient).
But I think that staff run plots and other player run +Events and plots are not going to satisfy you unless you're just looking for tabletop ish stuff (and you know, that's fine too, really!). I do think it helps to try and adjust to seeing your PC not as the prime element of your enjoyment. (Or maybe that's just a personality thing for me, dunno.)