Sluice gates aren't a common thing on the list. This weir that has protected the nearby city of Magdeburg since its introduction in 1875 and won prices at the Paris expo, then got used as an example for other sluices to do the same around the world. I find this worthy already. Some pictures on the site show similar sluices closer to the cities which for me would be better visits; however, as this is the first sluice it's important by itself. This sluice gate is a bit of a drive from Magdeburg and there is nothing else nearby. The building at the opposite of your parking lot is still in use by the workers so it's not a visit. At first sight I figured that's a small museum/visitor center, perhaps even a ticket and I took the wrong exit to reach but no, it's off limits. You do want to walk over for more plaques and another view onto the sluice from that side of the river though.
Overall I took maybe 30 minutes to see everything and is only because I walked along both sides of the sluice gate with the opposite side not allowing a pass-through. One also cannot visit the interesting top which I find a bit sad but I understand there are people that would leave trash or even damage it if left unattended. After all this gate is useful. At least, I think so. When I was visited the water was very low and nowhere near the gate. Same for the picture.
If you passing through the area it's a worthy stopover but I wouldn't make it a travel goal by itself.