If the receiver has another HDMI input, hook the AppleTV right into the receiver. That way you can use the non-video benefits of it (like listening to music) without having the TV on. That's Apple TV to Receiver to TV instead of Apple TV to TV to Receiver. Ideally, a Receiver is the central hub/brain of a system, so the goal is usually to connect everything to it vs. making it a last link in any chain. The original AppleTV was called an iPod for your television. Take advantage of the iPod side of it (which doesn't even require a television): airplay target or stream music to it from your Mac, via apps like Apple Music, Pandora, etc.
Use overkill HDMI cables for the connections- like 8K 2.1 HDMI. They don't cost much more but will basically futureproof the cabling parts for the next decade or more.
In AppleTV, video settings, you can turn on match frame rate and match dynamic range so that stuff shot in various formats pass through to the TV... though THIS could prove to be a weak link if the receiver is too old to pass them through.
If you prefer the TVs or the Receivers remote as a master remote, you can train AppleTV to work with either. Usually this is done by clicking a button to put the remote in a different mode like cable (box), AUX, or similar. And then you "learn" it in the Apple TV remotes menu. After that, you can basically put the AppleTV remote away (though this option will not make the other remotes into Siri remotes if you want voice controls).
If the receiver is new enough to work with CEC, you can turn that on in AppleTV, Receiver and TV so that turning on AppleTV automatically turns on receiver and television... and turns all off when you are done watching.
What else are you seeking? I presume you have good speakers connected to the receiver, ideally at least about 5.1 so you have solid surround sound. Good sub for bass? Good center channel speaker for voices?
If you have your own media (videos, music, photographs), the Computers app (orange icon) is great for accessing all of that from a single source. IMO, it is much better than accessing it through the AppleTV app "library" because- among other things- you are not bombarded by advertising. Check out Computers, turn on home sharing on your computer and enjoy access to everything you have accumulated as owned media in a
single app. It is often overlooked by people with new AppleTVs but it is
the second most used app at our home.
Apple TV connected to TV through a Receiver hooked to some great "dumb" speakers is a fantastic source of video & audio. We greatly enjoy ours just about every day.
If you live close enough to get free HD over the air (antenna/rabbit ears) and/or subscribe to cable, look into the incredible
Channels app and
Silicon Dust HDHomeRun boxes which bring free over the air and/or cable into AppleTV much like a good DVR or cable box (minus the leases). Over-the-air can get you the big 4-5 major networks at quality better than cable for free. In that same spectrum, there can be many subchannels in lower quality running classic TV shows (some favorites of ours are
MEtv,
AntennaTV,
LAFF,
Catchy,
Heroes & Icons), special interest, etc.
Punch location info into the box at AntennaWeb and it will show you the free channels you can probably get. If you'd like to see what's on those channels, try
ChannelMaster to see the current grid guide. Seeing all the freebies may motivate you to put up an antenna or get rabbit ears or similar.
Channels is our most used AppleTV app.
If you have Apple-oriented friends, consider getting a
phone or iPad mount for the TV so you can use the new
Continuity Camera feature with the FaceTime app. It works much like FaceTime on an iDevice but you see the other party on the big screen... more like life size instead of micro-size on tiny iDevice or Mac screens.
My guess is that "old" receiver may not be able to pass through latest standards like HDR10+ (which may or may not matter because your TV may or may not be able to show them), so you might want to start thinking about a modern replacement for that Receiver as a next AV purchase. But for now, it should all look and sound fantastic. Enjoy!
Ask questions if you need more.