I think when we talk about network speed, we must distinguish between usage scenarios and not generalize. There are different specific reasons behind different scenes.

For example, the slow loading of the paper mentioned by the topic owner may be due to the low export bandwidth of the domestic per capita international network.

Moreover, gamers often say that the network speed is slow, which means that when playing games, the delay is high or it is easy to drop the line. This may be because the network access conditions used by users are not reliable enough, or the game operators are not reliable enough, or it may be a problem of the local network environment of users.

If users who often watch videos say that the network speed is slow, it is likely to be buffered frequently during the playback process. It is more likely that the video website computer room is overloaded.

For download users, slow internet speed probably means slow download speed. This is more related to the richness of files on the Internet and the size of network bandwidth.