Being an IGL requires managing risk, and sometimes a leader will call a risky play, like the one you mentioned, purely for the purpose of catching another team off-guard. We, as spectators, might condemn such a call if it fails because we had the information, but were it to succeed the opposite is also true.
It's fair to say that you can understand fundamental mistakes by watching as a spectator. I've seen numerous instances of pros making terrible decisions during retakes/post-plants that they should know not to do, with or without information to tell them otherwise.
But with that said, what you're talking about is essentially hindsight. You can't always play it safe in a match, because sometimes that's what's hindering you from overtaking another team.
You're not entirely wrong, obviously. There are certain kinds of calls that don't make a lot of sense, but we also don't know what the actual reasoning was behind that call. A leader does his best to understand what he's been given and turn that into a proper avenue for success. If a player communicates information incorrectly, it could lead to the scenario you're talking about. We can't presume to know all of those decisions without being there in the first place.