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This might hold true if you’re talking about desktop browsers, but it’s a different story on mobile, particularly in rapidly growing emerging markets. Both network latency and large JS payloads dramatically affect user experience on low powered devices, and if UX isn’t compelling enough, there have been plenty of studies showing the real financial costs of slow web pages for businesses that depend those websites to bring in customers.

I’ve personally spent many hours doing performance analysis, triage and remediation on websites built using modern tech stacks that had inadvertently exchanged UX for DX. Too much JS sent over the wire can definitely tie up the browser’s main thread for whole seconds even on desktop, though in my experience it’s much more common on mobile. This situation can be difficult to correct depending on the abstractions, organization and overall architecture you chose early on, and code-spitting and dead code elimination won’t always fix what’s broken.