Availability of content on Amazon and iTunes is very country specific. In my country, there are no TV shows available at all, and the movie selection isn't stellar either. Half the stuff I want to watch just isn't available for purchase at all.

And availability keeps changing! You want to buy a movie that was available last week, and it's gone!

It's so frustrating...

It's certainly not changed significantly.

iTunes never had the offering OP claims tbh, but it also hasn't significantly moved from what it had.

In the US, very little if anything. Overseas, it depends greatly. I tried to use Amazon Prime in Norway, and it's a mess. The user can see all the titles, but can only play a fraction of them. I even got shafted after purchasing a movie because it wasn't available to stream to my location (this was on console so bypassing with a vpn wasn't a 1-click thing like on PC, that is if amazon hasn't blacklisted most major vpn providers to begin with)

tl;dr - doesn't work that well, depending on where you live. I've become reacquainted with torrent sites these last few years.