Depends on the game. If the playthrough is ruined when choosing the wrong option then a walkthrough is a must.
If the walkthrough only saves you from discovering what to do on your own, that it is not needed at all.
If the walkthrough is Forced at the start of the game, forcing you to do certain actions in a certain way, that you find in a 100 other games. Then the game WILL get deleted and never looked at, let alone played EVER AGAIN.
Depends on the game and how linear it is, but 90% of the time, yay.
I believe majority of games do benefit from a walkthrough of some sort, or walkthrough like mechanics (for example, in novels, marking, or informing the player, if by selecting a choice, you'll miss something).
Though i think pure walkthroughs should be player made rather than developer created. As devs have a skewed, and biased perspective on what their game is, and where will be points of contention for the players.
It depends heavily on the game, i find fun to figure out stuff in say, Succubus Prison, but some games have some bullshit in them. For instance Lobotomy Corporation has a mechanic where you always fail to interact with an abnormality if it is within your camera's sight, with no indication of such, i looked it up because that was pretty bad design and i do not regret it. Besides that, if you don't want to sink 900 hours to get each ending and all achievements in some games, you're gonna need an walkthrough.
I hate missing out on content, if I need a walkthrough to not miss something I like having one. If it's a sandbox game I don't mind fucking around for a bit trying stuff out before trying a walkthrough though, and if it's impossible to miss out on anything I'll generally power through