If anything, it's just the opposite. The 'rules' (again, this should be understood as patterns, or perhaps rules of thumb) practitioners implicitly rely on are far more complex than most theorists are implicitly comfortable with. This is why bookish music theory was mired for centuries in pointless discussions about acoustics and ratios, or some incredibly weird formalisms for representing meter, whilst practitioners got on simply focusing on what sounded good.
(The 'Rule of the Octave', which is the kind of rule I'm pointing to, was quite exceptional in being explicitly taught in actual published treatises about music - and even that was practically forgotten later on; it's not usually taught in "introductory music theory" classes even though it arguably should be!)
What "there are no rules!" is kinda the excuse for music theorists to keep on working on a field that has had so far little applications on how music is created. Maybe yeah on how some people learn it, but that's it. It's basically them admitting that actually successful musicians usually work under a set of rules and techniques so simple from the theoretical standpoint that the whole field gets invalidated.