A pro will notice things about implementation that interfere with the content, while the layperson often can’t articulate it even if they sense it’s not quite right.
I especially hate it because the best alternative I can suggest to someone who doesn't understand tech well enough to manage such a thing is to just keep on trying to keep up with whatever fancy kit Web developers are working with these days. Which invariably means sending ever more money to Comcast. And regularly giving money to Best Buy to replace a computer that isn't really broken; it just can't keep up with the latest fashions among ad networks and reactjs developers.
Wait, how often are people peering over your shoulder to even notice? Have been a programmer for 30+ years and no one has ever made an observation either way about my screen responsiveness...
For those unaware, an empty house can go untouched for decades in NYC, but once it develops a broken window, it is ransacked and squatted within hours. Small failures invite large failures.
I'm not saying we should all code in assembly and c and make sure our arrays are memory aligned and pointers efficiently used, etc. etc., but we should also not just stop caring about code quality for "productivity" sake.
Then realize that level of a connection is more common than you think. You never hear it elsewhere because those users just don't use your site, because they can't.
That's not a particularly uncommon speed, either. If you pay too much attention to statistics about "average" home internet speed, you're likely to be optimizing for only the top quartile, because the distribution of home Internet speeds is highly skewed.
The modern interwebs is a bloated mess...1 minute plus loading times is more common than not.
Super Mario for NES, a full commercial video-game, weighs in at 32KB.
Half of humanity has intermittent and very slow Internet access and old hardware.