My view (similar to yours, it seems): adding an interface means adding complexity. That complexity will have benefits in some cases, but outside those cases all you have is the cost of the abstraction. And as has been said, everything can be solved by adding another layer of abstraction, except having too many layers of abstraction.
So the question becomes: in your case, does it offer an actual, concrete benefit, to offset the cost of added complexity?
My view (similar to yours, it seems): adding an interface means adding complexity. That complexity will have benefits in some cases, but outside those cases all you have is the cost of the abstraction. And as has been said, everything can be solved by adding another layer of abstraction, except having too many layers of abstraction.
So the question becomes: in your case, does it offer an actual, concrete benefit, to offset the cost of added complexity?
Thanks for your insight. Ps. I love the saying about solving things with abstraction :-)