Whether guides are good or bad depends on how you use them. For example, the vast majority of games can EASILY be beaten without any guides, just through trial and error (the few exceptions that might require a guide are things like Runaway 2 which have some weird issues guides might help warn you about). Guides to beat the game are kinda like handholding, so I never use them (only two guides I've ever used for the story were for FF1 when replaying it recently after 15 years and for the aforementioned Runaway 2 since there's some progression-related items that glitch out and I didn't know that so got stuck without the guide).
Once you beat the game though and depending on the game, guides can be EXTREMELY important. For example, the main three game series I play are Pokemon, Monster Hunter and Kingdom Hearts. For Pokemon you need to know stats, moves, mechanics, etc. to make the most out of the Pokemon you breed along with stuff like learning about IV inheriting and so on, so while you can play endgame (meaning online battling) without all that it will make an enormous difference. Monster Hunter and Kingdom Hearts on the other hand have a ridiculous amount of drops or items found from enemies and other places with some being extremely rare, plus need to know advanced mechanics and so on to truly master them both. For example, for MH you need to learn in-depth mechanics of weapons, monster weakspots, damage calculation, hidden mechanics, in-depth skill effects, dodging mechanics and so much more that the game doesn't even remotely try to explain, so without guides to learn that stuff you will literally never master the games. For KH, knowing what enemies are found where and in what conditions they drop the items you want to synthesize things to help you get better (eg: the same enemy can drop VASTLY different items depending on where you encounter them), knowing dodging/blocking mechanics, knowing enemy attacks and so on are what will make you improve, that's why once you truly know the game you can go from the usual 50 hours it normally takes to beat on easy difficulty (you'll be around lv60) to only 3 hours on critical difficulty (aka very hard) while only being lv1!
To sum it up, guides aren't really needed for story and might ruin your enjoyment, but depending on the game, once you beat the story, guides might be the one thing that will make you truly master a game.