No reason you should feel compelled to use the machines over free weights.
With free weights there are far fewer exercises to learn, in a typical gym session I will do at most four different exercises, often only two. You are already used to using dumbbells, the only catch to using the barbell at the gym is that the barbell weighs 45 pounds. It’s best to use just the barbell without any weights on it until you get used to the exercise. Imo it is wise to spend a few weeks just getting used to the motion and developing a full range of motion before adding significant weight to the barbell.
Weight machines can be risky compared to free weights, some brands of machines are safer than others. Personally, I like the plate-loaded Hammer Strength machines but fewer gyms are carrying that line of machines these days.
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