Reducing your word count can serve more purposes than saving money with your editor or meeting contest guidelines. The more you hone your writing style, the stronger your writing becomes.
Editing tools, if you use them correctly, can help writers identify certain areas in which they can improve. While I don't suggest depending on these tools, they definitely don't hurt. The key is to know why you're agreeing with whatever the tool says and only making the changes you agree with. Never assume the tool is right. Many times, it may not be. Then, if the change is something you've had to do more than once, add it to your style guide so you can be consistent with your flaws and attack them early on in future works.
Idioms have their purpose. When you're using them intentionally, it's okay, but when you use them because you can, you might be cluttering a great scene with a cliché.
You can take critique and do many things with it, but there are several ways to interpret notes you receive from your beta readers, alpha readers, or editors, and even more ways to recover from it.
Tracked Changes looks intimidating at first, but don't fret. With a few pictures and tips, navigating your marked-up document can be easy.