Is optical mostly a waste of time versus Ethernet?

Almost forget what this was about.  Ethernet ports are transformer isolated. They won't pass low frequency noise. They can pass high frequency noise, but its a transformer. It will reject most common mode noise. How hard can it be to isolate that part of the circuit from the DAC and analog?  Seems every piece of electronic test equipment has an Ethernet port today. They don't seem worried.  Someone mentioned jitter. I know this crowd is anti Audioscience, but tests are tests emotions aside. Jitter shows up as distortion. Tests I have read have been laptops and basic router/switches into DACs. I don't seen any added distortion from ethernet.

I see a lot of expensive Cat-6/7 cables. Those are shielded. The shields are connected at both ends. That does sound like a recipe for a ground loop that did not exist before.

@theaudiomaniac so, you called me out. What is wrong in any of my posts?

to your posts, I would add while UDP does not provide reliability at the transport layer, it leaves that to the higher level protocols. Which is huge headache, and probably why Roon ultimately switched to TCP.

Or they switched because they were not providing high level correction of lost packets, realized it was an issue in some networks, and went the TCP route to fix it since most home networks today have more than enough bandwidth unlike when they developed their product.I don't know the answer. I don't think you do either. Roon networking is for local connectivity, though it does provide management and access for external services.  Most do not put a wrapper around UDP to guarantee transport. If you are going to do that, you go TCP. For UDP, any number of feed-forward and error correction schemes are used for media to provide coverage when packets are lost and some minor retransmit schemes have been used where low latency can be maintained, but full guaranteed delivery makes little sense with UDP when TCP exists.

If you felt called out, perhaps consider not making absolute statements that are incorrect nor holding yourself up as absolute.

You are both very knowledgeable and I'm grateful those standards mentioned aren't my decision to implement. The OP asked if there were solutions to improve noise, clocking, jitter, etc and were they beneficial. Some Audiogon members report improvements, others not so much. Who is right, maybe everyone. Each system is different, each environment is different.

The OP is an adult and can choose to check these out or not.

@theaudiomaniac you specially called me out. My posts are accurate, networking is as close to absolutes as you can come.

Your comment is more or less exactly what I said…

As for wrappers around UDP, most applications do build some sort of reliability wrapper around it. In the case of Roon, they specially call out the need to support DRM, which requires reliable transmission. 
Other applications like gaming have indicators of packet loss, which is a reliability wrapper, if you didn’t, the game would either crash or just hang if you lost connection somewhere. 
VoIP also have call quality indicators, another form of reliability wrapper. So, it is more common than not to use UDP and a reliability wrapper.