High D/E ratios could mean things - 1) The company is efficiently using its shareholders capital and ROW will be high 2) Or company is taking too much risk and could be in danger of bankruptcy by defaulting on interest payments.

In many industries such as technology this ratio will be lessers than 1 since tech companies hardly have any debt.

I would think that lower the inventory requirement of the company, lower the D/E ratio. Since high inventory companies like retail, manufacturing etc will need debt for working capital. Retail and manufacturing companies have a D/E ratio around 1.8x.

For finance companies the concept of D/E is used very differently. Since finance companies typically borrow money to lend it out again. So they could typically work with much higher D/E ratio