I don't like dark themes because aside from straining my eyes, the dark color denotes a negative aura. With light theme, it would be refreshing to the eyes depending on the combination of colors. But very colorful webpages is also uncomfortable with the eyes. In short, themes are like food or beauty that is in the eyes of the beholder.
i think both light and dark themes can be great depending on how you build them. some dark themes do give off a dead aura but sometimes they can give off a peaceful aura, WHle light themes gives off a welcoming aura
I personally prefer light but I believe going with both is the best decision. Just let members switch between them. For example, at day I could use my light theme and at night in the dark, I could use my dark theme so my screen isn't too bright when viewing the site.
It really depends on the person who is looking at it but for me I prefer dark ones because it somehow correlates with classiness and elegance so that's why but I don't see anything wrong with light ones, it is actually pleasing to the eyes and most of people will prefer that features.