Your average "web scale" cloud system with Node and lambdas and VMs and distributed databases galore feels slow and clunky as hell before it's even under load, to those of us who remember "bad" old LAMP stacks running on a 1U server.
Not that I want to go back to that, exactly, but our performance expectations have gotten really screwy.
[EDIT] or, hell, take "Web 2.0". Piles of code and frameworks and shadow DOMs and shit all chasing and touting "performance" while full-page-loading low-JS sites like Craigslist and Basic HTML Gmail (or HN) leave them in the dust. Know what those are doing? Handing HTML to the browser and letting it render it. No JS render step, no fetching JSON then passing it through Redux and then making twenty function calls to eventually modify a shadow DOM to later apply to the real one. The browser is fast. Your JS is what's fucking slow and eating all my memory.