Must be a pretty old case study when it mentions a "router-hub topology". (BTW, router-hub means router[s] and hub[s] being used, together, to built a network.)
Sounds like this case study finds some "major flaws in its design" which would be addressed by replacing hubs with switches, the latter VLAN capable.
Generally a switch is usually a good replacement for a hub, with or without using VLANs. Using VLANs can make it much easier to implement some logical topologies that would be much more difficult to implement on hubs (or non-VLAN capable switches).
Today, though, modern LANs often use L3 switches which eliminate most, if not all, routers. I.e. some common LAN topology design generations were router and hub, router and switch (with or without VLANs), and now L3 switches (with or without L2 switches).
Today you might find it difficult to find any one selling new hubs.
An example of some of these device types, within the Cisco product line.
An L2 switch, 2960 series. (NB: some models support some basic L3 switching.)
An L3 switch, 3650 series. (NB: can also be used for just L2.)
An router, an ISR 4xxx. (NB: some models support L2/L3 switch modules.)
BTW, although on LANs, L3 switches are often used in lieu of routers, at the WAN edge, routers are still commonly deployed. This because they are often feature richer than a L3 switch (although also often "slower" for the same cost).
