The ideal number of exercises per workout session is 3-4 exercises. If you select your exercises appropriately and train them with sufficient volume and intensity, this will be more than enough to make great progress.
Focusing on fewer exercises per day is critical because it forces you to focus on what really matters. Many workout programs include far too many exercises, which can become counterproductive.
Whenever you lift an object, climb stairs, or bend down to tie your shoes, your body recruits many muscle groups at once to perform the task. That is why you shouldn’t focus on muscle groups. Instead, you should focus on movement patterns.