This is a pragmatic piece of Fowler on the rather dry topic of Object-relational mappings - in short, the attempt to marry an object-oriented code base with a relational data base.
Usually you’d get enough early success to commit deeply to the framework and only after a while did you realize you were in a quagmire - this is where I sympathize greatly with Ted Neward’s famous quote that object-relational mapping is the Vietnam of Computer Science
What Fowler refers to here, is Ted Neward’s article “The Vietnam Of Computer Science”
I consider the ORM hate uninformed and misguided at best. Just like any other technology not all of them are created equally there are better ones and worse ones. I have used Entity Framework Core for years and have almost no complaints but If I only knew ORMs like NHibernate then I might have a different opinion.