What is worse than shooting shitty? Sure, there are a ton of things. But when your life depends on it there is nothing worse! I have used different grips through out the years. From being a newb and gripping it how "felt right" to now where I have a solid grip on the gun with the thumbs forward hold. The tea cup grip is when you hold the pistol with either hand and then lay the gun into the off hand like it were a plate and you were holding a cup of tea. Hence the tea cup comparison. You might have seen this hold in....well...TONS OF MOVIES! It is a huge favorite among actors and directors in movies. From Matt Damon in “The Departed” to Matt Damon in "Bourne Supremacy" to Matt Damon in "Bourne Ultimatum". Oh, wait. That might be a Matt Damon thing. But still there are tons of examples, too many to point out. But I will point out that Matt Damon makes lot's of guns movies and is an advocate to limit access to firearms for citizens. Back to the point.
What happens with this grip is the main hand will move, very easily mind you, left and right. So and movement will alter the aim of the gun. It is easy to see in a demonstration. Hold your cleared weapon like this, then have someone push your main hand to the left or the right. Even just move your hand left or right. It is easy. If you hold it with the thumbs forward hold this is dramatically difficult compared. If you are using this tea cup hold and are having inconsistent groups with the same weapon and ammo, I would say it might be the grip. Try and have a grip like below.
We broke free from the tea sipping British Empire. So get away from the tea cup hold! Unless if works perfectly for you. Sometimes different holds work more positively for some people. You might be part of the 1% or your just a baller like DeadPool!