The jet engine simply throws molecules (mass) rearwards (velocity) and the reaction to this is what drives the engine in the opposite direction.

One popular way to describe this is this I learned at school: you stand on a wheeled cart that has a pile of bricks on it. As you start throwing some bricks rearward off the cart as hard as you can, the reaction of force required to throw them will slowly push the cart forward.
To maximize the obtained speed of the cart you can throw more bricks per second or increase your throw velocity or use bricks with more mass.
With this analogy we can clearly relate to a "top speed" being reached for the cart relative early as a person cannot throw that very fast.

So even for a reaction type propulsion there is a definitive top speed just as a DF or prop.

The rpm of the turbine can be left out of the equation, its just a result of other internal design parameters such as blade area and other geometrical dimensions, flow efficiency, sealing between the stages and EGT to name a few. The same goes for fuel consumption i.e efficiency of the total design

my two cents