Five lines of CSS isn’t an extraordinary amount of development effort.

Not all websites are built the same, some might require more than just five lines of CSS. Add to that QA to make sure it works. And purchasing the device(s) to test that it really looks fine (plus setting up remote debugging if it needs adjustments) or writing something to replicate the notch behavior. It's one more thing to support in already many things we have to think about when doing web development (different browsers, OS, screen sizes, orientation, available features, ... and now the notch).

Apple could have used the space around the notch for some browser UI for example and spared us the extra effort to make our websites look good (or even be functional) with that notch. At the end of the day, it's their customers that are benefiting from a good/better browsing experience.

Not to mention the development time they forced Google to waste when they implemented the feature on the new Pixel. (Plus LG, Essential, OnePlus, ....)

Are you saying Apple is responsible for the time that takes to copy their design? That is certainly an interesting take.

Also maybe there's an argument to be made about this being time invested in a feature (notch support that the OEMs were already implementing) rather than wasted.

I was being sarcastic about it being a monstrosity that caused depression, as stated by parent comment. :-)

Haha sorry that went right over my head