Comment by mschild

A mix of both. There are large number of websites that are inefficiently written using up unnecessary amounts of resources. Semi-modern devices make up for that by just having a massive amount of computing power.

However, you also need to consider 2 additional factors. Macbooks and iPhones, even 4 year old ones, have usually been at the upper end of the scale for processing power. (When compared to the general mass-market of private end-consumer devices)

Try doing the same on a 4 year old 400 Euro laptop and it might look a bit different. Also consider your connection speed and latency. I usually have no loading issue either. But I have a 1G fiber connection. My parents don't.