When someone tells you "the Wi-Fi is slow," they're handing you a symptom, not a diagnosis. Nine times out of ten, the actual problem is somewhere else entirely — the upstream connection from your ISP is saturated, the firewall is doing too much deep inspection, there are four APs all on channel 6 fighting each other, the DNS resolver is timing out, or someone is running a giant Time Machine backup over the same uplink. The Wi-Fi is just the closest thing to blame, because it's the part the user can see.
The reason this matters: the fix is usually free, but only if you're looking in the right place. A network engineer arriving at "the Wi-Fi is slow" and replacing the access points has accomplished nothing except spending the customer's money. A good first move is much cheaper — open the controller, check channel utilization, look at the upstream link's actual throughput vs. its provisioned speed, see whether a single device is consuming 80% of the bandwidth, check DNS response times. Five minutes of reading dashboards tells you whether you have a Wi-Fi problem at all.
The mental model that helps: think of the network as a series of pipes. Wi-Fi is the last pipe between the user and the wall. Plenty of things can go wrong in the wall, in the pipes behind it, and at the source the pipes connect to. If the water pressure at the kitchen sink is low, you don't replace the kitchen sink. You walk back through the pipes until you find where it actually drops, and that's where you fix it.
In practice, the most common real causes we see are: an underspec'd or congested ISP link (especially when the company has grown but the internet hasn't), a single uplink port on the switch saturated by something noisy, channel overlap on the APs (especially in shared buildings), and DNS misconfigurations that make pages feel slow even when the network is fast. None of those is glamorous to fix, but all of them are fixable. The next time you hear "the Wi-Fi is slow," resist the urge to buy new Wi-Fi gear. Start with the dashboard.