Discerning a difference between streamers is difficult...only me or common for all?

You’re not crazy.  The sonic differences in upgrades become more subtle once you have high quality components in my experience.  I have moved from integrated components to separates over the years.  The biggest differences were in the speakers, DACs, streamers, and CD players.  The source and end point components.  Less with amps and preamps in my experience.  I moved from a Blusound Node N130 as a streamer to an Innuos Zen Mk3.  I noticed a difference.  Beyond a quieter background I found it stayed connected to my wi-fi better.  I use a cable from my router directly into the unit.  I have my equipment setup in such a way that I can A/B test when I try new components.  If I don’t hear a noticeable difference I return the new and more expensive gear as you did.  Trust your ears.  

I think one should just be happy with whatever sounds good. It doesn’t matter if one has a $500 streamer or $5000 streamer. And that applies to speakers and other equipment. Enjoy the music and you are not crazy.

You have a broad spectrum of replies that reflects the following homilies

”Price is what you psy,…Value is what you get”….. and … “One-size does not fit all…”

MT EXPERIENCE

Visit your fave bricks and mortar audio dealer and do a bake-off audition between a budget unit ( say BLUESOUND); and a high-end build streamer/dac.

Assuming you have the requisite resolution capabilities with a full high-end audio system, the step-up unit audio performance will not be insignificant.

Ethernet cables also matter..Direst Ethernet cable from router to your streamer/dac connection is always a step-up from wireless. Upgrades to premium cables with silver over copper construction and properly insulated sheathing with Telegartner connectors do matter .

Quality build linear power supplies (internal or external) are another big-time performance uptick.

You do get what you pay for. The DAC and the Streamer sections both need premium design and build quality … and that is a function of price too. Many believe that the secret to a good DAC lies in just choosing a “high-end” converter chip. But,,,,we know that the essence of the musicality also resides in the line signal processing stages, the power supplies (transformers, filtering, regulation,… ), the digital signal processing before conversion, the quality of the key components: clocks, transistors, capacitors, op amp upgrades etc.

TAKEAWAY

Starting out in the digital ,streaming world , it’s frequently a fork in the road pathway between an option that is “ good” versus “ good enough” . There is a marked-difference.

Just buying blindly and hoping is poor…. Hoping is not a strategy for a better option. Budgets are usually in tension with best wish lists that may invoke compromises.

I had two great sounding systems in my house. The main system was substantially more expensive than my second system. My main is using an Auralic g2.1 (G1.1 at the time of comparison) while my second system was using a Node. 
here’s the odd thing to me… when I put the node into my main system the SQ notably decreased, as in immediately evident. However when I put the auralic into my second system I didn’t notice really any bump in SQ at all. It sounded great with both and I never had any desire to upgrade the node there. I wish I could pinpoint why this is, but it just is. I’m happy with each in their respective places.

Ten years ago I bought the original blue sound vault. At first it was good enough. Over time I went back to vinyl. About a year ago i started to convert my system to optimize streaming. I bought a holo spring 3 level 2 dac and used the vault as a  streamer. The improvement was more than subtle but not huge. When the new blue sound nodes came out I bought the "older" n130 node and used it as a streamer. The improvement in sound quality surprised me. Timber, tone, depth and separation of instruments improved. I thought the node/holo spring 3 combination sounded very good but a tad warm. I bought an innuos pulse. The change in sound was subtle but important to me. There was more sparkle to cymbals and a little more sizzle to the high notes of a French horn. What surprised me was that I could  now understand what more of what the singers were saying. Not a big difference, but enough to keep the innuos. By the way the innuos app is very usable for someone who does not like computers.