I agree with that.
Even when performing weighted dips last in my chest routine, I still feel the strain on my shoulders. Since you are placing yourself in a biomechanically inefficient position.
Are you coming back from an injury is that why you cannot perform the bench. Or are your shoulders naturally weak. In any case I recommend some form of rotator cuff exercises. Even if its just one exercise per week, will help to make the shoulders structurally stronger.