How to stay interested in Eve Online?
Solution 1:
Ohai! Srs Internet Spaceship captain, here!
EVE is ultimately a game about setting your own goals and taking satisfaction in achieving them. Nothing else matters. Not your killboard score, nor the amount of ISK in your wallet, not even your spaceship fame. Not unless you make them your goals. And believe me, those are the really boring ones.
On goals themselves, there are two broad and inaccurate categories for them: in-game and meta-game goals. Former would include anything that somehow affects the gameworld - accumulate X ISK, build a corp with Y members, etc. Latter would include visiting every system in the cluster, collecting one of EVERY item (looking at you, Entity) in the game, figuring you what the heck is the big Sleeper mystery or learning everything there is to learn about every game mechanic, effectively becoming an living EVE encyclopedia.
IMO, metas are much more interesting, but to each their own. Again, I want to reiterate the importance of taking satisfaction in achieving your goals.
This should give you some ideas.
Solution 2:
You already addressed one of the ways to get ahead in EVE - join a corp. I played EVE a long time ago but never got into a corp and got lost and bored easily, so I quit. I recently went back to EVE because I got tired of the same theme park MMOs, and wanted to tackle a harder learning curve.
Two things that kept me around (currently taking a break because of new job) were my interest in industry and the fact that I found a good corp in a good alliance. We do everything from PVE to PVP, but we are not so hardcore that you feel pressured to do anything. It is a lot easier to get interested in the content when there are people to support and help you learn how to get around in game.
EVE is hit or miss with many people. Some people just hate the structure while others love it. It is easy to get overwhelmed by the learning curve and discouraged by the mentality of some of the more hardcore players. But if you do find a place in EVE, it can be very enjoyable and pretty addictive.