I didn't ask if you thought all DACs and amps sounded the same. I asked you to consider why they sound different (if you do perceive a difference) and then consider if some of the same factors might apply to streamers.
Based on your response,I gather that you haven't actually tried any upscale streamers. I won't change your belief through this discussion. May I suggest you try one in your system? If, after then, you decide there's no benefit, then you'll have a data point on which to base your opinion.