Those of us "of a certain age" remember only having manual focus. It was really easy to see if something was in focus because you usually had split-image focusing. When the images lined up, you were in focus. Most digital cameras, at least the ones I have used, are difficult to focus visually alone, so some have a focus indicator light in the viewfinder that tell you when you are in focus when using manual. Some will go into a magnifying mode to allow a better view of sharpness.
So, no, you are not wrong that manually focusing a modern camera is not easy.
That said, I only use manual focus to lock in what my autofocus has done, especially when shooting video and I don't want autofocus to "hunt" during a shot.
My usual focus method is: I set the focus mode to single point, and keep it on the center. I use that indicator to pick my focus point, focus by holding the shudder halfway, then re-compose if needed before fully depressing the shutter. You can also move the single-point around to pick the subject, but I 've used my method since long before pre-digital days, and it serves me well, so why change.
There all manner of focus modes now of course, but I just don't trust "intelligent" focus to know what to focus on.
I made up a set of cards with various themes or ideas. Mostly sky. Out of focus. At my feet. Mystery person. Close your eyes. Etc. I ended up with about 40. We’d meet somewhere and pick a few random cards and all interpret the theme in our photos and compare over coffee or a meal.
Another fun one was to take photos inspired by or interpreting song lyrics.