Bicycle lights aren't blinding anybody. At least none I've ever seen. They're powered by little batteries usually.
The subject at hand was whether they flash or not. Not their brightness, which I've never heard anybody complain about.
They are much worse if they flash. That blinds and disorients. Even after they pass you won't be able to see anything for some time.
If you're somewhere without any other lighting and your eyes have adjusted to the darkness, then I can understand how they might seem bright. But I'm not really sure what you think the solution is. They're already vastly dimmer than cars, but make them any dimmer and the cyclist won't be able to see the ground and it won't be safe.
E-bike rentals don't have anything adjustable, and where I am, they're quite fixed at illuminating the ground.
Maybe there are people with e-bikes who can draw a lot more power and have higher-powered headlights? Are you talking about e-bikes specifically? But it's just not something I've ever seen. I'm certainly blinded by vehicles while cycling under certain circumstances, but I've never once in my life felt blinded by cyclists or even anywhere close. That's why I'm so confused by what you're describing. When you say "blow away your vision from half a mile away easily", I honestly can't even begin to imagine what you're talking about.
Stuff like this:
https://www.amazon.com/s?k=bike+headlight
You can even see people posting pictures of the light where it's clearly illuminating 10' up the tree on the side of the path.
I'll start paying more attention -- I'm curious now -- but I can still definitely say I've never felt blinded by a bicycle, or even close.
And the lights in that photo seem fine -- the road is pitch black just 20 feet in front. The tree is getting a lot of light reflected from the road and grass. The lights don't seem to be illuminating anywhere even close to as far as car headlights illuminate. None of that looks anything like what car headlights produce.
People do it for safety, but it doesn’t help. I literally can’t see where you are if you have a bright light shining in my face. The same thing is true if I’m in a car. As long as you have lights I can see you. If your lights are obnoxiously bright and especially if they are blinking you have succeeded in making people want to harm you, not increased your safety. The drivers who aren’t paying attention will not be more likely to see you if you are just a blinding glow of light.
They absolutely are. They suffer from the same phenomenon as car headlights. They're often poorly aimed (at an upwards angle instead of downwards) and have adopted an insanely bright white colour. I frequently yell at other cyclists when they blind me.