Test wired versus wireless
Connect a computer by Ethernet when practical and compare performance. If wired service is also slow, the issue may be the internet connection or modem rather than Wi-Fi coverage.
Router placement matters
A router hidden in a basement corner, cabinet or utility room may struggle to cover a large home. Central, elevated placement usually helps. Dense walls, floors and neighbouring networks can reduce signal quality.
Mesh is not magic
Mesh systems can extend coverage, but node placement and backhaul quality matter. Adding too many poorly positioned nodes can create more complexity without improving throughput. For businesses or larger homes, wired access points can be more reliable when cabling is practical.