Look at Mark of the Ninja

I'm terrible at stealth games. In metal gear solid, I constantly have to shoot my way out of failed sneaking operations, and I don't feel bad because even tho it was ridiculously tough to win such encounters in the old MGS games, the recent ones - such as peace walker - left you with good options and choices in case you knew you had to fight at one point or another. I've heard many good things about Mark of the Ninja and decided to give it a shot.

No amount of fine tuning will fix bad players
This game plays great, the controls are spot-on and will allow you to do pretty much whatever you want - with some exceptions when contextual menus get out of hand and you can't do a specific thing because you're too close to another, dropping guards in vents comes to mind - the character moves precisely where you want to and you get tons of informations from the world.

You know the radius of the sounds you're making, you know if you're hidden or not with simple visual cues, all of the possible information that you could need to pull of successful stealth missions is readily available. Vision cones, being able to peek out of doors and vents, contextual menus for everything... That being said, I didn't have a great time playing it because I seem to be terrible at it. Jumping behind a guard only to have him turn around and shoot me, or simply miss the assassination prompt - terrible with a mouse/keyboard, but I'm not holding that against the game - and punch at the air instead of being a stealthy ninja. I'm not going to blame the game if I'm terrible at it, of course, but not being able to play it in any satisfactory way is kind of a bummer for me.

Woops

How I would fix this
Add more combat-oriented options to the game so you can get out of sticky situations easily. Maybe some difficulty level toggle to be able to play through the game with easier stealth scenarios and more dispatchable enemies. Or some kind of Ez-Gun like in metal gear solid where you become harder to detect and regenerate life at all times to make the game more easy. Why not allow you to stab with your ninja sword instead of punching? After being spotted 20 times by a guy I had to follow, trying to complete challenges, I decided Mark of the Ninja was too tough for me.

Get points!
You get score for everything you do in MotN, sneaking past an enemy undetected, killing him after, to finally be hiding his body. Secret items hidden in the levels also net you points, so do some challenges where you need to get to a specific point without triggering some manner of traps. You also lose score when you raise alarms - which is a disapointing because your total score is bummed and at this point you're better to just die anyways and restart. Points are used for leaderboard purposes, which I do not care about and to unlock new abilities and item powers, which I do care about.

Challenges and point totals you need to get

You have a few objectives in each stages, one is to get a certain number of points, that unlocks some upgrade points, you also need to do objectives such as breaking a certain number of lights or not being spotted at one point in a mission. Maybe doing these objectives was what I did wrong in the missions I struggled. For example, the mission where I was spotted 20 times it was because I had to hide enemies in dumpsters and doing so placed me in obvious disadvantages. You also need to find three scrolls per level, each with a little poem or story on them.

How I would 'fix' this
Add another difficulty level untied to leaderboards where you don't lose points for raising the alarm - thus removing the apparent need to restart the level each time you mess up.

The upgrades are nice but not earthbreaking
You have a few items in MotN, darts that make noise and attract enemies, smoke grenades to run away of tight spots or block laser beam, spike traps that impale anyone stepping on them, bugs that noisily eat enemies alive - or dispose of corpses. You also get new takedown moves such as hanging from the ceiling or through grates or from the ground. I'm not sure if I'm entirely at fault here but it happened to me a few times where I didn't know which move I had and tried to attack an enemy from a location where I couldn't do anything. All and all, my problem is that I'm not seeing anything here that would change how I tackle the core gameplay, and that's what's important.

It's not really customisation, it's just adding things to your arsenal and you mostly will use them all anyways, adding more uses to the flashbang or a bigger radius to the smoke grenade won't change how I play the game.

I usually associate screens like this with deep character customisation, but not really in this case.

How I would fix this
Add more variation to the moves and different items that would change how you play the game, anything to make the game easier for different kinds of players, maybe stealth enhancing  techniques or straightup fighting  upgrades.