I see too many overcomplicate their workouts by adding too many exercises to build muscle. The reality is most can have great results with one and two good exercises per muscle group in each session. Now, let's break down why this works.
For most individuals, even for those into it for hypertrophy-related gains, doing one or two exercises per muscle group during a workout is good enough. You don't have to use every machine in the gym to yield results. Instead, focus on doing two to six sets per exercise. This allows you to get into a rhythm with each set, improving your form and muscle engagement as you go.
For instance, if you are doing your chest, off of jumping from one chest machine to another, focus on the bench press and dumbbell flies. Pound those exercises with a number of sets, and you'll see that by the fifth or sixth set, you are losing the groove. That is your sign to move to the following exercise, reestablish that groove, and proceed with the work.
You don't need to hit every muscle group, every single day. Instead, you want to aim for two to four sessions per muscle group a week. This gives your muscles time to recover while continuing to progress.
You can work your chest and back on Monday and Thursday, for example, while working on your legs and shoulders on Tuesday and Friday. With fewer exercises but higher quality, you will see progressive growth without overtraining or burning out.
One of the better aspects to this whole approach is that it keeps the routine fresh. Since you're only using a few exercises at any given time, you have plenty of options to choose from when it's time to switch things up after a few months. Variety can be added later with no feeling of overwhelm.
In this case, after three or four months of doing squats and leg presses for the legs, one can incorporate lunges and hack squats. That way, it can be a little more challenging without adding a whole lot of variety to things. Note that varying workouts will lead to continued muscle adaptation and better overall development of the muscles.