Seems like Tidal has nowhere near the selection of Spotify.
Hopefully it gets better?
We can hope they will get a bigger selection over time, but I think you could get a better answer contacting Tidal, rather than Denon 
Maybe they have a support where such things can be suggested.
Denon has never mentioned that Spotify will be considered for streaming.
But they did mention 4 or 5 streaming services overall, so there’ll be lots of choice for many genres without having to resort to Spotify
Sure but they all have a monthly subscription
I think Beatport link will be the best for my music but everyone will have a different favorite Im sure