And in all cases, I realized that I stink as a player.
It's ok. No one is perfect. I enjoy reading your posts, and I still think you're cool. At least you're not me. You have that to be thankful for.
Anyway,
Seems like your concerns are:
1) Little to no imagination.
2) You can't decide what your character should do.
3) You don't think ahead.
4) You don't naturally take to puzzle solving.
Let's address these points one at a time.
1) Little to no imagination. IMO, it's quite possible your imagination isn't being stimulated. You're not being presented with an intriguing, interesting situation. Read me the intro paragraph of a D&D module, and trust me, I don't give a rat's what happens.
Solutions:
* Who is your character? What does he care about? What makes him mad enough to fight? What makes him love enough to risk his safety? Is there a woman he loves so much that he would smash Aton Winston Peale's head into a table just to make her notice him? Would some punk ripping up an Imperial flag make him fight 10 guys just to plant a solid right hook on that punk's jaw? Does he care about the lives he's taken or the men he's maimed during his military service and adventuring career? Did he ever get married? Why or why not? Does he regret that his space murderhobo lifestyle took the best years of his life and he doesn't have anything to offer a woman except a bunch of scars and half-remembered stories? Does the first thing a woman says to him start with "Yah, you buy me drinky, I know you got credits, Impie!"
* Do the scenarios you're presented with in a session discourage any in-depth development of who your character is? Do they focus on the next tactical exercise or saving Charted Space again? Do these challenges and situations mean ANYTHING to your character, or are they just another ammo bill? Where is your character's heart?
* Does your character give a steaming cup of Basic about the people he's in the scenario's life-threatening situation with? Are they the brothers in arms that he'll give his life for before letting them down? Or are they the people he wishes would just step on a mine so they would stop talking?
* Connect your character to these feelings. Connect him to the dread of yet another life threatening situation that he's gotten himself into. Why? Patriotism? If he doesn't fight for the Imperium who will? Does he need that one big score? Is he getting back at life every time he pulls the trigger on some nameless thermal image in his combat armor's heads up display? If he earns enough money on this job will it be what he needs to get that manor estate out in Five Sisters? Give your character feelings and reasons and these will tell him what to do. All stories are human stories.
2) Can't decide what your character should do.
Well, again, it depends on the scenario, but as always, there comes that time when your character has to settle up his bar tab or get out of his bunk and go take care of business. He's in a situation. What kind of a guy is he? Is he strong and tough? Would he go somewhere and ask around, knowing he could take on anyone who doesn't like some stranger asking questions? Or is he older, more bookish, retiring, with his startown-brawling days behind him? Maybe a character like that would check records, speak to admin people, check starport logs, with a cask of Zilan wine under his arm. Again, who he is guides you. If the ref says, wull, you have to go here and do this, then you're in a pickle, because it doesn't matter who anybody is, you have to go there and do that. But... how does your character, with his feelings and personality, react to that? Would he say ok let's shank these guys, get the macguffin and get paid, or would he say mayne, I don't want to be here any more than you do. You don't mess with me, I don't mess with you, and I'll just get rid of this macguffin for you.
Again, a lot of this comes down to the kind of scenarios you're being presented with. A lot of Traveller is something like "A random stranger bugs you to do something illegal before being hustled away by the police." No reasonable person would listen. They'd even say, thanks for getting that freak away from us, officers. Refs need to help the players by presenting the characters with situations they'd reasonably take an interest in.
When you're character is in a situation, think through every obstacle that might be in your way, then think of what you will do to overcome that obstacle.
Example: Get the macguffin from an isolated mountaintop villa
Obstacle: mountaintop
Solution: grav vehicle, climbing gear, ground car and be ready to force the road.
Obstacle: Guards.
Solution: Take them out. Lethal or non-lethal? Research their capabilities. Get appropriate weapons. Figure out tactics. Watch them. Frontal assault or stealth? Spy on them with space binos from the opposite mountaintop.
Obstacle: Security systems.
Solution: Check them out, see what's available on that planet. Bring a specialist in electronics or mechanical, depending of the tech level.
You get the idea. The ref had to think of all this, so he wants you to figure it out. He'll be glad to tell you what you discover.
3) You don't think ahead. Solution: practice thinking through what obstacles there might be and possible solutions, as above. Listen to what other players are saying. I'm sure there's a lively discussion about what the characters could be up against and what to do.
4) Puzzles are usually boring. Like, okaaaaay, there's an alien pyramid, yeah man! Any reasonable person would say well, call an effing archaeologist, what do I effing look like to you? But, for some reason you have to go in there. Well, golly. So there's your Navy vet, standing in front of this crumbling alien edifice in a corrosive atmosphere thinking how in Iphegenia's comfortable shoes did I get myself into this? And the first officer says, quiet you, self-actualized womyn are talking. Well, stuff like this is a holdover from how what we'll politely call 'scenarios' used to be designed, and a lot of refs still do it. To boil it down to the chickenskins, it shakes out to be go-here-and-do-this. This means you just have to go touch it. Interact with it. Walk around in it. Look out for typical ref surprises like tripwires, energy fields, face hugging xenomorphs, trapdoors, and magic items- I mean, Ancient artifacts. Be careful. Inspect everything. Say the traditional chant at every room and corridor: Ohhhhhmmmmmm, magicitems/secretdoors/checkfortraps. The environment or location is meant for you to explore it, so check it out. Have the other characters with you, so they can share in the joy of the ref's little surprises. Just make sure someone is in back with a rope and a rescue harness.
After all the cool little surprises, you'll usually find the Answer to the Mystery, like the data chip, the alien control room, the boss battle, or whatever it is you've gone through hell to get.
Anne McCaffery (her sci-fi stuff)
Dinosaur Planet was cool, but Pern was meh. Skip Marion Zimmer Bradley. She was an utter monster in her private life.