It can be interesting seeing what is often seen as a common task can make computers of that vintage suddenly start to struggle when they can seem to do so many other tasks just fine.

One common thing I've experienced is browser-based video conferencing. A lot of chips in that generation didn't really have a lot of hardware accelerated video codecs, so a number of things have to rely on pure software and thus really crank the CPU. Meanwhile a cheap modern mobile chip can handle those same video streams without even breaking a sweat, due to having accelerators for those video codecs.