A distributed system is slower than a laptop or phone by definition of “distributed” which entails a network which has a higher latency than your local system. It’s not about raw speed/latency as much as it is about volume.

I used to compare distributed system with freight trains vs F1 cars. But there are a ton of low latency distributed systems too like your LTE network.

The key factor is how much data is shared by how many endpoints. Having these two very high makes it for very hard problems. Like streaming high definition events to millions of people.