I have way too many 3 putts.
I sometimes miss 2 footers.
Why do I suck so bad at putting?
Are your three putts the result of bad lag putting? Missing too many short putts? Hitting approach shots that leave difficult putts? Are your misses on short putts due to line, speed, or both? Do you typically miss on the same side every time?
Sorry for all the questions, but saying "I suck at putting" doesn't give much to work with.
Do you practice putting? Admittedly, I don't practice it enough. You can work on accuracy at home -- just putt the ball straight at whatever target you set on the floor. For gauging distance, you need to know what the greens are like that day, so take 10 minutes before your next round and hit a couple dozen putts on the practice green. As good as I am about making time to go to the range before a round, I'm really bad about making time to go to the practice green. Makes a big difference.
I know many people that are just practicing without a real purpose.
They may roll 100 balls and every one of them is a bad roll and they don't even really know the difference. They have the misconception that if they make the putt (on makeable putts) it's a good roll and if they don't it's a bad roll.
A good roll doesn't guarantee making putts but it certainly increases the chances and the opposite is true of bad rolls.
FWIW, I've taught AimPoint to both "linear" and "non-linear" golfers. It works well for either. You just have to know how to use it with each type of player (not that any player is exactly 100% linear or non-linear).