Discogs allows non-commercial private use of their data, and they provide monthly data-dumps of the entire database as well as APIs to access their data. There are in fact numerous companies selling products that rely on Discogs data (SongKong, mentionned previously, being one of them), so what is “non commercial” is not very clear…
Metadata management is a complex topic. It should not be, but it is.
Being able to see who is playing on an album seems to me like a pretty “basic” request. Why is the information missing from so many “digital” services ? When we had LPs or CDs, you could look at the jacket and find the information (most of the time). Why should that information no longer be availble simply because we are accessing the music differently ?
When you watch a movie, or use IMDB, you are interested in knowing who directed it, who is acting in it - if you like an actor you will look up what other movies he/she has played in.
That does not mean you cannot enjoy the music if you know nothing of who actually made it - but being a little curious can be rewarding (and part of the “discovery” process).
Well, with most streaming services, and unfortunately with a significant number of cases in Roon as well, that is simply not possible. You would think that adding a simple list of credits would not be so complicated, but I guess it is.
Unfortunately, and I do not know why, music digitalization has simply not addressed this correctly. The labels who pay no attention to this, the streaming services who pay no attention to this are not “respectful” of the works they are publishing.