From users perspective, when I see the lightning icon on my search results I feel happy because it means that the page will show me it's contents as soon as I click it.
It means that the website is not going to show me white page for 15 seconds then start jumping around, changing shape and position for another 30 seconds until everything is downloaded.
I hear all the ethical/economical/strategic concerns but the tech community resembles the taxi industry a bit, that is, claiming that a tech that improves users experience significantly is bad for the user and must be stopped politically instead of addressing the UX issue that allows this tech to exist in first place.