Do you mean far-UVC, around 222nm? It seemed like the major issues were the sources being expensive, the sources being from dubious vendors with no standard certification (I would be concerned that my “222nm” source might have a lot of inadvertent emission at other wavelengths), and possible damage over time to whatever you aim it at.

The bulbs only last maybe 1000 hours as well which combined with their price narrows their usage.

Yes. Those problems seem relatively easy to fix compared to the immense benefit of a significant reduction in disease transmission across the board.

Do you actually know they are easy to fix?

Here on hacker news we have a long tradition of software people claiming that some property of a tangible world, like ‘no such material physically exists’ are easy to fix.

"relatively easy to fix compared to the immense benefit" is what I said. Even a few percent reduction in cases of these illnesses would likely be worth tens of billions of dollars for the economy every year. And it could also be justified as defense against bioweapons. A hundred billion dollar program to improve cost and establish certifications could easily be justified if efficacy and safety are good enough. And I'm certain at that level of investment (much lower, probably) cost and certification problems would be very solvable.

isn't UV light dangerous for people?

perhaps there's certain wavelengths that kill viruses/bacteria but don't increase cancer risk?

254nm is used as part of GUV and it's not good for people and black out blinds are used in hospitals where they are installed when sanitising. Far UV 222nm is not damaging to humans that we know of but it's a peak of destruction for viruses, bacteria and fungus.