What’s wrong with YouTube? Most people use it and are familiar with it. Create a video with a static image or repeating slideshow if you only have audio.
Lots of folks use SoundCloud, and to a lesser degree, SoundClick, for posting just audio.
All sites will do additional compression of your content because bandwidth costs money and “free” means the business is managing costs as well as not trying to push higher quality than the connection supports (in the case of video). Plus the vast majority is listeners are watching/listening on phones or 25-cent earbuds.