Whats wrong with straight ticket voting?
The main problem is that its impossible to select good candidates by voting for parties instead of candidates. Even though political parties are a practical part of the process, voting based on stereotypes of what that party represents can really backfire in the voting booth. A knowledgeable voter should know where their candidate stands and vote for the person and not the party. Even candidates in the same party can sometimes have very different approaches to dealing with issues.
The other issue is actually voting against yourself in some elections by straight party voting. On the ballot it is easy to miss the races that only have 2 candidates running instead of 3. So if you are a Republican and vote straight ticket but do not go through all the races you may miss one that is a Democrat vs Libertarian. The same thing goes for Republican vs Libertarian. Because that race was skipped no vote is recorded at all for it and you are essentially assenting to the majority. A Libertarian may actually be closer to what you want for that office but you missed an opportunity.
Work towards electing representatives we can be proud of and not parties we just follow blindly. Showing up to the ballot booth is a big step but without being informed about who is on the ballot you can't be a whole voter. Vote smart, vote informed.