"Intelligence" is a mostly meaningless word. There is no consensus definition
Nonsense. Intelligence is the ability to formulate an effective initial response to a novel situation. Not everyone would agree on the exact wording, but most people would generally agree on what intelligence means. Most people would also agree that a dog is more intelligent than a chicken, a monkey is more intelligent than a dog, and that (most) people are more intelligent than monkeys. "General intelligence" means an ability to solve general problems, but intelligence can also exist in domains. For instance, in the domain of playing chess, computers are more intelligent than people, even though their general intelligence is lower than an insect.
no testable or falsifiable phenomenon associated with it.
Not true. There are plenty of repeatable tests for intelligence. There is not universal agreement on every aspect of that, but some people can clearly demonstrate a superior ability to solve a broad range of problems, in a measurable, quantifiable, and reapeatable way.