There are no “buttons” on an iPhone screen; this is by design.
I tested several apps on my iPhone (13 mini) and none require a swipe from the left edge rightward to “go back.” This can be achieved with a rightward swipe from the center of the screen.
On Apple products, it’s more about the gesture than the actual location where you take the action. Other than some very specific gestures like opening Control Center, unlocking the phone, and seeing notifications requiring the gesture to begin at a particular location, things like navigation or zoom are recognized anywhere on the screen.
Gestures are a key way for people to interact with their touchscreen devices, eliciting a close personal connection with content and enhancing the sense of directly manipulating onscreen objects.
This is from the iOS Human Interface Guidelines published by Apple. More specifically, under Best Practices it states:
In general, respond to gestures in ways that are consistent with other apps. People expect most gestures to work the same regardless of their current context.
It sounds as though the developers of the apps you are interested in/use have strayed from this design tenet. From your comment that it’s pointless to contact the developers means they will never receive the necessary feedback to improve their apps.
It’s highly unlikely you’ll find an app to fix what other apps should have implemented in the first place.