If you have a large space that can't be covered with a single powerful router, or there is no possibility to install a router centrally, or you can't run Ethernet cables throughout the space, or maybe the walls are made of thick material that causes interference, the good solution would be implementing mesh networking.
A mesh network has a really good feature of self-reproduction: even if one or more nodes are not working or removed, a mesh network will redistribute data via another channel. Also whenever a new node is added, the mesh network can discover and configure new device.
Most of the times a good mesh networking kit will fix the issues with WiFi dead zones and will provide you with an even signal all over the space. And again, it is a no brainer to set such system up. However it doesn't make your network signal faster. Of course it will feel faster, because of the multiple access points and devices finding the signal faster and staying connected. A network with multiple access points can well handle a lot of devices better than one WiFi router. However a lot of spaces like single family homes and small businesses don't have that many devices connected at once.
A WiFi extender is a good addition to your existing router before implementing a mesh network. Such decision will cost you less than getting rid of everything you had and investing in a mesh networking kit. The least expensive mesh kit is around $400.00, and sometimes it may be an unnecessary spending.
Here you can find more info on mesh networking, its purpose and how it can be useful for you.
To see the WiFi dead zones of your home or office, use NetSpot survey app that helps you manage your WiFi network in the most efficient way.