Star trek online is unusual for an MMO; sure there is the pointless boring grind. However, STO also has a series of about 50 special unique missions per faction which are done in order, constitute the plot, and will take you from level 1 to level 50. They are listed here http://sto.gamepedia.com/Episode
So you can choose to ignore the grind, play those missions as if it was an offline RPG, and when you finish all the missions quit the game. This was my intent, however I hit a snag halfway through the federation plot missions. One bad enough to justify quitting. (not that the missions were terribly well written to begin with)
This is one of the worst "quests" in RPG history
First a bit of background, there is a race called "undine" who is infiltrating various factions using shapeshifting and then starts wars between various factions to weaken them for an undine invasion. When you get to this mission you had already encountered and fought them about 4 times or so.
You are supposedly off to stop the development of some superweapons by the romulans; you are being accompanies by a FLEET ADMIRAL who arranged this mission. First you clear out the ships guarding a space station, then you teleport down with an away team.
As soon as you teleport to the base you are told by the fleet admiral who is with you for some reason "this is NOT how we federation does things but use lethal force, we must stop their super evil subspace weapons!"... ok fine...
Enter first room, kill a bunch of enemies labeled as medical doctors; their screams of death and rage at your unprovoked attack on a medical facility make it ridiculously obvious that they are peaceful researchers... scan the crates, nothing but medical supplies
The obvious undine tells you those trixy romulans put stuff in the box that is tricking your scanners (you are not allowed to open the crates and verify).
She then suggests you try a data terminal for proof of her claims... look at terminal, purpose of station is "medical research and discovering ways to identify undine infiltrators". At which point it is so blatantly obvious that the so called admiral with you is an undine. But you are not allowed to accuse her.
Try "where are the weapons" on the data console... permission denied. Admiral tells you the data would be at the commander's personal console.
Proceed to butcher doctors for 10 more minutes, reaching the final room where the obvious undine says "kill everyone and leave no witnesses, the romulans mustn't find out that it was the federation that attacked here (as if the warbirds fighting you couldn't have sent out a message as soon as you warped into the system...) you have no choice but to do it.
Then scan the consoles, find nothing about weapons... commander of station teleports in with a single aide (I have a 6 person away team armed with weapons that have a stun setting), he ACCUSES me of being an undine for destroying their work. I have no option but to murder him and then...
THE BIG REVEAL "mwhaha, I was an undine all along! instead of maintaining my cover as an ADMIRAL in federation I am going to reveal myself to you for the lulz and then kill you, and then take the place of the romulan doctor we killed! oh and no way could I have brought a second undine to assume the role of the person we just butchered, I will do so myself discarding my wonderful admiral position for that".
Then after a slight beating the undine takes on the appearance of the good dead doctor, calls for help from the romulans, gets beamed up by romulan ships that came out of nowhere... who proceed to IGNORE being told he is an undine infiltrator and proceed to die under my hand (because shooting to disable is not allowed in this mission even though you have done so hundred of times in other missions). and the undine got away somehow even though you killed all the romulan ships.
This is one of the worst "quests" in RPG history, and it is completely unskippable, if you want to finish the plot missions you must finish this mission exactly as described above. So screw you STO, I quit.