Some apps do have uninstallers, which remove everything. Others have instructions on their websites telling you all the files you need to remove. So those are the first things you want to look for.
Another option is to email the developer and ask the file names and locations of everything the app saves on your system
But, barring those, I'll add my own endorsement of Find Any File—it's great. But the problem with relying on it is two-fold:
(1) You have to be careful not to accidentally delete a file with a name that sounds like it belongs to the app you're deleting, but in fact belongs to another app (or, worse, to a system file).
(2) Many apps install files with names that don't contain the app name, so it's impossible to identify them as belonging to the app.
There are aftermarket uninstallers, but MacWorld tested them back in 2010, and none got rid of all the orphan files:
It should be as easy as dragging and dropping to the Trash. But uninstalling Mac apps is rarely that easy. That's why there are uninstaller utilities, which claim to get rid of every last vestige of a program. But do they really work? Joe Kissell does some testing to find out.
www.macworld.com
Here's a review of the apps available in 2022 that do this:
You can speed up your Mac and improve performance with a Mac cleaning app. We review CleanMyMac and other apps for deleting files and memory hogs on a Mac.
www.macworld.com
It seems what's really needed is a program that tracks all and records all files added by an app at the time the app is installed. Thus it knows where all the orphan files are when it's time to uninstall it.