According to a statement they put out a few days ago, they're not currently using user uploads to train data, but their license permits it in the case they do in the future -- so don't panic about your uploads already being in a database, but remove them if you don't want them to be in the future.
As far as Bandcamp as an alternative, be careful uploading covers even with your own instrumentals because you also need to have the rights to the song's score because the score and the specific audio of each performance are separate copyrights. I don't know of any other good pure audio platforms, so your best bet currently might just be Youtube unless you want audio-only for some purpose.
Also seconding Sake's post above; it's not about user's wants at all, it's always about money. Never trust a platform or brand to have your best interests in mind; they'll sell as much of you as they can get away with.
