There are many reasons for poor putting but
First, you need to understand what a good put is. A put with the right speed that starts on the line you intended it to start on is a
You may have noticed how many different putting grips there are on tour. These are not typically used to provide more comfort but to provide more stability.
You can see below some of the grips used on tour. Justin Rose has done well with the pencil grip. Many of the top players have different grips. The reason for the different grips is to help overcome a bad motor skill movement in the wrist or poor technique. For me, I rotate the face open under pressure so my left hand is low and rotated
The primary keys to a good putting grip
Excessive wrist motion changes the face angle and also encourages the shoulders to decelerate. Find a grip that immobilizes your lead wrist and you will put better. If you have access to plastic knives you may want to try this. Put on your glove and then place several plastic knives in the back of the glove until the wrist feels immobile. Hit a bunch of puts this way and try to feel what a stable lead wrist feels like.
When you first try this don’t be surprised if you hit a few puts short.
Try a few of the grips below and see which helps you keep the left, lead wrist stable.