There is no app with Perfect "All Available" music.
Spotify has great plenty of millions of tracks, but still some tracks may become available or or unavailable due to right holder decision. It is not Spotify decision what gets delivered to Spotify or what gets removed from it.
I think OP is talking about the "10 k limit of Your Music", here is the "feature request" post with over 1000 kudoes. One of the comments in that post states the following:
Well this answers my question about why I was saving stuff then next time realising it hasn't been saved. But just thought it'd report that I got a message today when I tried to save something, it began, 'Epic collection friend. ' then went on to say Your music had reached its limit and I had to delete things before I could add anymore.
Go vote for that "feature request" and Spotify can possible wake up and increase this very small limit of their core feature.
If you like using the "Your Music" feature have in mind that you are LIMITED to 10 000 tracks. If you want this to be fixed vote for this post
You really don't get the point. The point is that I can save/bookmark/like songs whatever it really is but this is limited to 10k. Why this limit? I am not actually saving anything. Basically what Spotify wants me to do is save all my albums as a playlist. This is not a great user experience and they should fix that. I have 28k songs in my iTunes Library. How do I switch my collection over? Probably Spotify would have to pay more to rights holders for saves, otherwise I don't see why this would be limited to 10k.