The key is to use tools like this selectively. I often use a style checker on my fiction, to highlight repeated words, sentence fragments, passive voice, overused words, and clichés. Most of the suggestions I ignore (particularly sentence fragments, which I use a lot in stories), but it's still a good exercise in making me consider whether I can rephrase sentences to be stronger or more interesting. Sometimes passive voice is what you want, but sometimes the sentence is better in an active voice; it's easy to overuse intensifiers like "really" and "very"; and there's a few other verbal tics that tools like that can catch.

Technical writing may be a bit more formal, but you still have to selectively apply suggestions from tools like this.

Having said all that, I find Hemingway Editor to be infuriatingly bad at this. It's terrible at actually editing, while it's a plain text editor it's not Markdown-aware, and it doesn't actually catch the sort of things I'd want such a tool to watch for (like "actually" earlier in this sentence). Its primary function is to harangue you about sentence length.