I just did this tour on an Oceania cruise a month ago, but saw Viking “lollipops” along the way. It is a beautiful setting and moderate walk until the last 30 minutes or so. Then it is fairly steep downhill, lots of steps that are natural rock so uneven. There is a railing. Not necessarily hard, but you do have to pay attention to your footing and the depth between steps.
We took a boat ride to Skradin (beautiful) for lunch (meh), and caught the bus to return to our ship. I would not want to walk back up the waterfall to a bus.
BTW…the bathrooms are quite a distance from the base of the falls, cost 1 euro and have no electricity which means no lights. I’ll let you use your imagination on that one. The people in our group who went to use the facilities were gone most of our free time.