Besides, when the law is ambiguous, it's very often because the legislature themselves weren't sure what they intended, and/or because the legislature had deeply divided views and arrived at ambiguous wording as a compromise, and/or because the legislature used their "somebody else's problem" prerogative i.e. they said "let's leave that for the courts to decide". Ambiguously worded laws isn't a bug, it's a feature!
Second, interpreting the law is a full-time job, and our legislators are already not doing the jobs they have. If we asked them to not do a second job on top of the one they're already in dereliction of, nothing would get done. Well, twice as much nothing would get done, if that makes sense. So, you need someone with the full-time job of interpreting the law, and it might as well be that judicial branch.
Third, legislation is often a compromise. If you go back and try to interpret what it was that people said during the debate which produced the language at issue, you'd have to decide whose voices carried the most weight, which seems very, very tricky. It's why legislation is written down in the first place: a single source of truth. Even if ambiguous, it's still less ambiguous than a transcript of extemporaneous debate.