I work at a small prop trading firm and we run 10x or even more leverage most of the time. Without leverage, we wouldn't be able to run the vast majority of our strategies.

Basically, leverage is immaterial: what matters is the risk of the strategy. A leveraged strategy could be less risky than an unleveraged one.

Things that you should consider when deciding leverage: beta exposure, correlation to the market, volatility of the strategy, and the risk adjusted return of the strategy.

A classic example of this is risk parity: risk parity uses high leverage but is often safer than a classic 60/40 portfolio.