Yes, there are upper limits, and things get difficult as you approach them. There are "softer" limits imposed by infrastructure capacities, "firmer" limits imposed by seaworthiness considerations, and finally hard limits due to material properties and the forces involved.

Others have covered infrastructure limits, so I'll begin with seaworthiness. Bigger ships are more fuel efficient due to the square cube law, and industry has pursued that advantage by increasing size dramatically. But bigger ships require more steerage way, and are less controllable at low speeds. They also need more power to overcome wind and current. They are hard to control in tight harbors and locations without sea room.

The final limit is materials. Humans approached the upper limits of wood ship size, and the biggest wood ships had considerable hull volume devoted to reinforcing frames, stringers, laterals etc. All necessary to deal with the unequal forces imposed on a ship's hull. Not only by wind and waves, propulsion, but by the inequal buoyancy inherent in making something pointy that will go through the water efficiently. There is less buoyancy at the thin ends than amidships, and over time and constant movement that causes wood (and metal) ships to "hogback", where the bow and sterm droop and the middle rises.

We never solved the issue with wood construction, we simply found stronger materials. First iron, then steel, and now higher strength steels.

But the bigger the ship, the bigger the forces, while the tensile strength of steel remains about the same. To prevent buckling under dynamic loads, more and more payload consuming reinforcement has to be added inside the hull, until like their wood forebears, it becomes impractical.

At that point, maybe we'll find a new material again, and start over with a brand new limit.