A company's assets are resources that it control. Resources comprised of what the owner/s put in (equity), and what lenders and suppliers etc., loaned or yet to receive. Hence, A = L + E.
So when you do these debt/equity ratio etc., you have to interpret it in the context of the business and its financial performance. So you'd want a company that can somehow use other people's money for cheap, or for free; but don't want to be in it if business condition deteriorate those debt aren't cheap and aren't free and you go bankrupt.
Remember you're investing in a business, not investing in some historical numbers or forecasts that will hit the dots as predicted.
It's safer to go for companies with strong barriers and established pposition - all because these kind of corp. tend to be able to keep doing what it has been doing without much trouble as far as you can see. It shouldn't mean you buy big blue thinking the world it operates in will be like it had so it's safe.
Reverse that and if you understand a business enough, feel confident about its future enough... its current financials can pretty much be ignored. Risky, but so are buying big and hold thinking there's no risk.