flashlight

Lights with modern performance and only a single mode don't really exist. Even lights that appear to be that almost always start out on a higher mode and throttle to a lower one. The main reason for that is that to avoid burning the user's hand and/or having a very short battery life, the output has to be relatively low.

If your flashlight has much less output than most of its competitors, you will not sell very many flashlights (unless you're Zebralight - normal rules don't apply to Zebralight).

Depending on why you don't want brightness settings, there may be some good options for you. If it's that the lights you've used change brightness when you turn them on and off, almost none of the lights flashlight enthusiasts like behave that way.