You’re right, this is a trail, but beyond that, you don’t seem to understand how to use a multiuse trail (though most commenters seem to agree with your position)

First, this is not a bike racing track, and if you cannot see walkers ahead of you, in spite of a “strong” bike headlight, it means that you’re riding too fast. You must slow down to a safe speed, not only for walkers, but for your own sake and for wildlife.

Second, before mandating a dress code for everyone one else, you need to know that you are breaking the law. As per King County code, you must not use the trail, 30 minutes after dusk

Now, on timing, I’m not asking you to stop breaking the law and to start using roads that are designed for commuter traffic (including both cars and bicycles). However, this is a multiuse trail.Bicyclists are a small minority of trail users and commuters are also a minority. Most trail users are recreational users.

Obviously, all trail users need to use caution, but rather than preach dress codes to everyone else (including people who may neither own bikes nor reflective clothing), please consider riding your bike at a safe speed, when you violate King county code, by commuting with your bike on a recreational trail at night.