What English learning advice sounds good in theory but falls apart in practice?

One of the biggest ones is "Just immerse yourself, and you'll become fluent." Immersion is valuable, of course, but many learners spend hundreds of hours watching videos, TV shows, and podcasts and then wonder why speaking still feels difficult. Understanding English and actively using it are two different skills.

Another common one is about memorising vocabulary. Vocabulary matters, but similarly to the previous one, knowing a word's definition does not mean being able to use it naturally in conversation.

What English learning advice sounded convincing at first but turned out to be much less effective than expected for you?