Your problem is that you are not used to using SLR. Generally, A gear is used, which is the aperture priority gear. In this gear position, the shutter is set automatically and does not need to be adjusted manually. What you said is similar to using an M file. M file is a manual file, not for you to take a snapshot, but for creation. If you need a high-speed shutter, use the S file, which is the shutter priority file. When setting the shutter, the aperture will be set automatically. For example, when shooting a runner, it is better to use the S file. If you shoot running water, you can shoot a silky effect by setting exposure for 0.5 seconds with S file. Come back and say a file. Most people want the background to be blurred, so they use a large aperture, such as F2.8, but the aperture of the best imaging lens is mostly F8.0, and it is better to use 8.0 when pursuing the best image quality. Of course, every shot is different. I'm talking about the big picture. If you want to take a snapshot, I suggest you turn on continuous shooting mode, focus on continuous shooting once with auto, and then choose another one later.

SLR is a little inconvenient to use, but the effect will still make you feel worthwhile. SLR photography is very skillful, which is also the charm of SLR. Use more and think more. I'm sure you will like SLR.

Personal opinion, I hope it will help you.