Reason why heavy aircraft are allowed to land but not to start I stumbled upon this article (German)
It says that a few of Lufthansas 747 are grounded at Twente airport. They were parked there because of COVID-19 at an aircraft recycling company.
Now the airport does have the license for such heavy aircraft to land, but not to start, which normally isn't a problem as they land there to be recycled.
Unfortunately the article doesn't state the exact requirements the airport doesn't fulfill. It just says something about safety issues. What could it be that allows the aircraft to land safely but not to start?
What could it be that allows the aircraft to land safely but not to start?

In the USA at least, to allow takeoff, a runway must be long enough to let an airplane reach takeoff speed, decide to abort, and reach a full stop.  That's longer than just landing.
The more ancient answer is: takeoffs are optional, landings are mandatory.  Refusing permission to land would damage Twente's reputation.
Even more ancient, before aviation, a ship in distress would not be forbidden to dock and ordered to head back into the storm.  (Only because COVID is mentioned, ships suspected of carrying plague are a different matter.  See the etymology of &quot;quarantine.&quot;)

Greg's answer uncovers the Dutch report, which quotes Meiltje de Groot hoping that the 747's could be scrapped (&quot;ontmanteld&quot;) in situ because of lack of demand, because of COVID's reduction of passengers, at Twente because they could land there with no intention of departing.