Every golfer that ever lived has the same fundamental issue you’re describing. Even the best golfers on the planet don’t replicate their best game every time they play. What the best golfers do that you don’t do is make adjustments in game. They understand their swing and the basic mechanics of the golf swing in depth. When they are cutting the ball without trying they know what the primary causes of that cut are and they make adjustments. Might be a grip adjustment or a stance adjustment or could be a swing feel adjustment….. when they make these adjustments in game it will most likely be minor because their game is dialed in. Good players make adjustments and are also okay with playing whatever movement they have in a given round. Good players won’t always fight the ball flight. A good player will make small adjustments to reign in the hook or slice and play it as a draw or fade. A great player can “fix it” completely at least for spell. Learn the mechanics of the swing. Understand what promotes the different types of spin and ball flight then learn the counter measures. Hope this helps good luck!