First, connecting a tunnel to a building doesn't make the building itself the same thing as whatever the tunnel connects to. By that logic, having a road to a hospital from a military baes makes the hospitsl a valid target.

I didn't watch the full video, but it sure looked like a long service tunnel, which tons of buildings have. Nothing that justifying destroying an entire hospital complex after they cleared it. Is the IDF unable to close a single tunnel going into a hospital?

Not to mention the part in bold from the article (found out I can get to the text at least through reader mode).

The Israeli military, however, has struggled to prove that Hamas maintained a command-and-control center under the facility. Critics of the Israeli military say the evidence does not support its early claims, noting that it had distributed material before the raid showing five underground complexes and also had said the tunnel network could be reached from wards inside a hospital building. Israel has publicly revealed the existence of only one tunnel entrance on the grounds of the hospital, at the shack outside its main buildings.

Yup, justifying destroying the entire hospital complex because one tunnel connects to a shack outside the main buildings. Really proving your point there!