I've watched the same routine play out in offices everywhere. The Wi-Fi is slow, someone buys the router with the best reviews, there's one good week, and then the complaints come back to exactly where they were. Sometimes it repeats every year, and the proof is a drawer full of retired routers.
The routine fails because it answers the wrong question. I start with where the access points go and how many there are, then look at what sits between them and the people using them.
Walls and shelving weaken the signal
Wi-Fi is radio, and radio weakens as it passes through things. Drywall takes a little. Brick and block take more.
Metal shelving, ductwork, a full storage room, and a commercial refrigerator all block it further. By the time the signal reaches a desk three rooms away, through a kitchen and a wall of filing, it can be a small fraction of what left the antenna, and no premium router changes that.
This is why I don't reach for one powerful router in the corner. In my experience, good coverage comes from placing several modest access points where the building actually lets the signal reach people, so every room that needs coverage gets it.
The problems you cannot see
Some of what ruins office Wi-Fi is invisible. Your network shares the air with the tenant next door, the forklift chargers in the warehouse, the break room microwave, and a dozen other sources. Two access points set to the same channel can interfere with each other and end up worse than one would've been on its own. A device installed years ago and never looked at again can drag every newer device down to its speed.
None of that shows up in a web review or on a spec sheet. All of it shows up in a site survey, where I walk the actual building with measuring equipment and map what the airwaves are doing room by room. That survey separates an installation designed for your building from one guessed at, which is why our wireless network deployments start with a wireless site survey.
Sometimes the wireless is not the problem
Often the wireless is fine and the trouble sits behind it. An access point can only hand out what the cable feeding it brings in, and I've found plenty fed by old cable runs or small switches daisy-chained under desks. Others sit behind an internet connection the business outgrew two hires ago.
The symptom points at Wi-Fi, and the cause is the network infrastructure behind it. Treat the symptom and you've bought one more router for the drawer, which is why the new router didn't help.
What a good setup looks like
A well-designed office wireless setup gets very few complaints. You get coverage in every room where people work and enough capacity for a conference room full of laptops and everyone's phone at once. A guest network keeps visitors off your business systems, and documentation means the next change is an edit instead of a fresh mystery.
Getting there is a measured process. We survey the building, design against the measurements, install to the design, and then run a second survey to confirm reality matches the plan. It takes more thought than a trip to the electronics store, and it costs less than buying a new router every year.
If your office has rooms where the Wi-Fi just doesn't work, or a conference room that fails the moment everyone is in it, schedule a call. Describe the building honestly, down to the metal shelving. In my experience the building is usually the answer.