There are a crap load of threads with this topic.
The debate can basically be summarized as this:
Pros to use a Smart TV over an ATV:
Lower cost, some smart TVs cost less than an ATV
Built-in and convenient
Buttons on TV's remote to activate apps
Cleaner set up, less wires and devices to hook up
Cons for Smart TV:
Lack of long-term support, Apps could stop working or be missing new features over time
Slower than ATV
UI isn't always great
Lack of privacy, many Smart TV OS sell user data without given an chance to opt-out
Pros to having an ATV:
Long term support
In Apple's ecosystem, some apps are available across different Apple devices
Homekit, iCloud, Remote app
Better UI, although this is subjective
Faster HW
Gaming* Due to dropping gaming developer support for tvOS, this is starting to go away as a "pro"
Privacy, Apple is pretty good here
Portability, taking an ATV with you during travel is nice, usually easy to set up in most hotel rooms
Cons
Cost is probably the biggest
Apple doesn't seem to care about tvOS nor the ATV, although this is just my opinion
The remote, the Siri Remote is not widely liked, but the newer remote cannot be used on many gaming apps
Not as clean set up
Higher video settings require a more expensive HDMI cable
Setting up for best picture quality can be a hassle, imo
Bottom line, since gaming isn't a factor for you, I would say that keeping your ATV around is a matter of whether or not you will use it. If you are not using it, then maybe get rid of it while you can get a decent price for it. The Apple TV is basically an overpowered, and overpriced streaming box. So much untapped potential, but pretty much back to being Apple's hobby.
Apple doesn't seem to care much about the Apple TV, and I wouldn't be surprised if Apple discontinues it over the next few years.