That author doesn't say Esri is a scourge; more like it's just generally bad to have only 1 provider in a space -- and that it's up to customers to change that by voting with their feet.
I think Esri is (and has been) in a very similar position to Microsoft's in the late 1990s -- having achieved market dominance, they feel like open source software is the biggest threat to their business. But I think the presence of QGIS is creating competition, which is nothing but good for the industry.
ESRI have similar network effect to Microsoft. No individual product is that great but taken together it is very competitive. And ArcGIS online is developing that network effect in a similar way to Office 365.
Also, the GIS space tends to have crossover between different departments in companies. You have a mix of IT departments, GIS specialists outside of IT departments managing infrastructure, data management, casual users etc. Each has a different budget and a different competitive environment. ESRI sits as a compromise between these different groups. Each group may be able to adopt a competitor but not gain traction outside their group.
I think Esri is (and has been) in a very similar position to Microsoft's in the late 1990s -- having achieved market dominance, they feel like open source software is the biggest threat to their business. But I think the presence of QGIS is creating competition, which is nothing but good for the industry.
(I worked as a developer for Esri for 15 years)