Why is it so hard? Plume-surface interaction plays a major role during the landing sequence. Most projects "test,test and more test" like the ones mentioned in the article, but they clearly have no idea how unforgiving the environment is. When the vehicle gets closer to the surface, the engine exhaust gets redirected upwards, accelerating regolith to ~ 1km/s speeds. Any sensitive hardware that is hit can easily be taken out. Additionally, the closer the vehicle gets to the surface the more difficulty landing sensors will have in looking through the induced regolith cloud.[0] NASA has been studying the problem through experimental and computational campaigns for a long time, but just recently has put significant resources into understanding PSI on extreme environments.
Also see the most recent first SpaceX Starship launch attempt. Widely accepted current theories about likely failure mode root cause involve exactly this sort of thrust ground interaction kicking up debris.
I am a huge proponent of sending robots first, to build safer landing and launch structures, possibly also bases or better places to situate bases.
There are many projects looking into building landing pads before any large vehicles, from both private and government. [0] is one I know. Interesting approaches but I have not seen anything yet that can withstand human class landers. These also pose significantly higher risks if the pads break up.
Edit: reference
[0] https://www.nasa.gov/directorates/spacetech/game_changing_de...