You can replace the sail on a ship, that doesn’t make it a new ship, or not the ship it once was. Chances are you prolly have to or should replace the rigging at the same time.
In this discussion, this is kind of a faulty analogy as you are replacing one thing with... the same thing. The better one would be to replace the sail with engine (two very different ways to achieve the same goal, which 5e spellcasting and cooldowns are).
So, if you replace a sailboat's sail with an engine, is it still a sailboat, or even the same boat? No, it is not.
