As it relates to the thread, Int-5 Sherlock Holmes could therefore be good at finding the hidden clues, but not as good at succeeding at ability checks related to deducing what those clues mean. But a player needn't ever make an ability check to do that if they can put together the clues and make deductions on their own since a player establishes what a character thinks anyway. The character might be wrong, of course, if the player reached an erroneous conclusion, and might not be able to confirm it prior to acting on it due to a subpar Intelligence. Notably, the high-Int character has this same problem. It's just more likely they will succeed on average without needing to spend additional resources.
Where Int-5 Sherlock Holmes might struggle is in figuring out how traps and secret doors work before disarming or opening them. But as far as recalling lore or making deductions in a way that might call for an ability check? That's something the player doesn't need to engage with if they don't want to. All they have to do is not declare actions that entail making deductions or recalling lore.
What are the common uses, if any, of INT in your game besides for some spell casters and for figuring out traps/secret doors?