Let me ruin some nostalgia for you:

Pre-macOS 10, there was no protected memory, so a misbehaving process would crash the entirely system.

Pre-Mac OS 8, there was no multitasking, so while a file was copying, you couldn’t do anything else.

Web browsers were vastly different in terms of behavior.

The visual quality of games has gone up drastically.

(This list is not exhaustive.)