SICP is a wonderul resource, but people already used to (not to say "indoctrinated" with) some knowledge from other sources may struggle to un-learn some old habits, or at least retain an open mind to allow for exploring alternative ways.

Note that the book teaches 1. a new language LISP/Scheme, 2. a new programming model (functional programming) and 3. a core computer science concept in various disguises (abstraction) - all at the same time! Some of the chapters require additional knowledge from other areas (hardware, compilers) or benefit from it (software engineering/API design), either as prerequisite or taught in parallel courses.

I found the book very valuable as the textbook at undergraduate level, but as part of a formal computer science university degree, where one gets help from lecturers, tutors, fellow students. It's definitely a demanding text for auto-didacts already stuck in their own (or Apple's) ways.