There are a lot of apps you can install and more you can sideload (Kodi etc), though it’s a bit walled into Amazon’s garden.
The iPlayer etc stuff, yeah I’ve got on Sky, though I’m considering ditching Sky. Prime stuff I occasionally use but not much. I might use more without Sky. Main thing I use is Plex to stream from my NAS. My smart TV has Plex app also, but the “smart” bit of the TV is shite, buggy, and outdated. I get reliable 5.1 over HDMI via Fire TV unlike from the smart TV stuff.
Kodi for dodgy stuff with little effort has been knobbled a bit I think, but Kodi does way more than that. It was intended as a home theatre media player.
I’ve found it’s a good quality audio streamer too. Better than my old Squeezebox hooked up to the amp. Got the Fire TV (box version) plugged into the amp direct and that feeds the video to the TV, and audio straight to the amp. For music it means using the TV as interface for selecting audio, or you can use the smartphone app to control it. I haven’t tried voice commands. You’ve then got Amazon music (there’s a Prime element of that), Spotify and whatever else, and my usual streaming from my NAS (I prefer Plex again as it does gapless playback, though I think I have to use the Plex extension in Kodi as the Amazon Plex app doesn’t do it).