We aren't there yet. So far, no matter how bright the bike light (and I have some of the top end ones), they are not blinding to an oncoming driver unless they look right at them - which is no different than car headlights. But, the brighter lights do make the cyclist more visible and that, given the extreme vulnerability of a cyclist by a car is a good thing.

I do agree that the next step is better beam management, but that conical reflector that puts light out and around is not wasted. That also is what helps to make one visible by lighting up surrounding objects and putting enough lumens (i.e. lux) out into a wider area makes the light more noticeable. Again, that's a good thing.

For example, if I created a light that took 4500 lumens and projected that out into a very narrow downwards beam with little to no spill, then I agree I would have an uncomfortably bright hotspot on the pavement and, collaterally, I'd have diminished visibility of my by other drivers from angles out of the beam.

What is happening, at least with what I see with my 2400 lumen wilma is that the beam is wider with more spill than car headlights would have so there is not an uncomfortable bright spot but there is a wider area with more lumens per square area (i.e. lux). I would suspect that the 4500 lumen betty is more of the same and, essentially, a similar beam with about twice the lux of my wilma. That would not be too bright and it would be very visible and not blinding but it would be bright.

J.