There’s some truth to that, but it’s also important that phonics lay down the foundation for reading, and let young readers identify the complexities behind the rules, and then internalize the meta-rules governing which rules apply where. It’s frustrating that tough doesn’t rhyme with though or through or bough (or that none of those others rhyme with each other). Or that many homographs aren’t homophones, to where you need to rely on context to know which pronunciation or meaning applies to words like “read,” “lead,” or “unionized.” Still, how else are you gonna do it? Lay down the basics, then layer on some exceptions that generally come in as loanwords (entree) or proper nouns (Xi Jinping), but always building on a foundation where new words can be encountered and pronounced. We can read and pronounce newly invented words easily, whether it’s slang like “mogging” or fanciful corporate trademarks like “Reddit.” We can deal with the exceptions as they come up.