I'm not saying it's impossible - glad to hear you've successfully implemented it in your workplace. I'm just saying that by-and-large it has the opposite effect to the stated intent.

If most examples of a strategy make things worse, and only one person uses that strategy to improve things, then going around saying "everyone is doing it wrong" rather than questioning the strategy isn't particularly sound.

I've build plenty of (small) client-side rendered UIs myself that lazy-load content; I know the trade-offs and I even believe I can achieve a performant outcome on my own. But that's anecdotal. In the wild, I have not seen a single major website improve perf. via lazy-fetched content rendering.