Sound quality issues streaming from Tidal vs CD

I am hoping someone familiar with streaming from Tidal might be able to help.

I have recently installed the Pro-Ject Streambox S2 Ultra, which is a small Raspberry Pi based network bridge. I connect this to my router via ethernet cable and to my Vitus DAC (which is part of the CD player) via USB. My CD player obviously outputs through the same DAC.

The sound quality from CD is so much better than the sound quality from Tidal (I am a Tidal Hifi subscriber).

So my questions are:

1. Is this just a feature of streaming via the internet, it simply is not as good as a good quality CD transport?
2. Or is it an issue with the Pro-Ject - would something like the Autralic Aries G2 (also a network bridge with no DAC) which costs 6 times the price of the Pro-Ject, improve the Tidal stream?
3. Or is it the fact that the USB cable I am using is an entry-level £10 cable?
4. Or is it Tidal? - would Qobuz sound better?

Any advice or knowledge would be welcome.
Please could you explain the difference between a streamer and a server?  

I do think the terminology in streaming is wanting.  Sometimes a streamer contains a dac, sometimes it doesn’t (when it sometimes is referred to as a network bridge) sometimes it is a pre-amp too, often it isn’t.  Sometimes it has a hard drive (is that when it becomes a server?).
A server run's Roon core and serves music to a player (or players). A player attaches to a USB DAC and streams music to the DAC from the server. Does that answer your question?

Qobuz has the best SQ, followed by Tidal HiFi MQA. You will need good bandwidth ISP plus good DAC to enjoy the music. they will sound better than Redbook CD in most case though sometimes I can't tall them apart. if you stream from PC, USB port can be noisy depend what PC your are using. If you have an Oppo 105 player. It has a build in app that allows you to stream Tidal internally (skipping the USB post and cable). 
1. no
2. yes and a G1 is also a good option.
3. a better USB would help and also consider AES/EBU.
4. no

The issue you have is electronic noise getting into audio signal via the streamer. 

Good luck!