What is the point of a building that produces infinitely without input wares and without any other requirements (not even spacial)?
That's not the question.
That depends on how you define "the question". I do ask this question, therefore this question exists, and unless you convince me otherwise, my answer to it is "the well is pointless in the current implementation of water".
The question is:
This also is not "the question", only another question that is neither more nor less valid than mine.
Why is it a difference if the building requires space or not?
In my opinion, every building is pointless unless it has some kind of requirement. This can be input wares, nearby immovables, resources in the ground, free space, or whatever. The well has no such requirement as the only applicable one (water resource) is merely a small boost factor, and the well still works way too fine if it is missing.
It's stupid to have to replace wells then all the time
The same is true for mines. And you can keep depleted wells around, since they´ll still produce for free now and then. You only have to build new wells now and then.
If you want that Widelands changes so radically
This is not more radical than your proposal: "It could be good to remove the resource water completely and let wells always run at 100%."
why don't you just do your own mod?
I already do, but most of the time I only play the branches I develop. Playing with further changes there is a high risk of getting bugs that would not happen normally (or not getting bugs that would normally appear), and I have to be always careful not to mess up the version control system with changes that should not be committed.
You don't even play online matches.
Perhaps I should stop implementing new features because I´m not going to use them in multiplayer games as well? Please explain the relevance of the ability and habit of playing online matches for the permission to make suggestions.