It doesn’t actually say that. It says it supports Wi-Fi, which it does, in the sense that the hub itself can be connected to a Wi-Fi network rather than cabled to ethernet. So it “supports Wi-Fi“ in the same way that a printer might “support Wi-Fi“ you can connect it to your existing Wi-Fi network. But it is not itself a Wi-Fi router, and it sounds like that’s what you need. So, yes, it would probably make the most sense to return it.
As far as a Wi-Fi router that will work well with a bunch of Wi-Fi home automation devices, there are quite a few options. The main thing to know is that most Wi-Fi home automation devices only use the 2.4 GHz band because it has longer range and uses less power. So all the other fancy stuff about the other bands probably won’t affect your home automation devices. Those other bands are important for your streaming devices like cameras and entertainment players and gaming systems. But not most home automation.
But other than that, it’s not really any different than any other use case for home Wi-Fi, so you can just follow any of the standard guides.
You may also want to check with your Internet service provider to see if they have a limit on the number of devices you can connect at the same time. Some do, some don’t, and some do depending on the specific plan you have with them.
(We used to think that 25 or 30 Wi-Fi devices would be enough for any home, back when we were only thinking about streaming devices, printers, laptops, and tablets. But once home automation enters the picture, as you have discovered, a single home might have dozens of sensors, smart plugs, light, switches, Etc. Each one is only using a tiny bit of Wi-Fi at a time, but you have to be able to make that many connections at once. )
Fortunately, there are a lot more inexpensive Wi-Fi routers these days which can handle 50 connections or maybe even more so you should be able to find something you can use. It’s just that’s not what the Aeotec hub is for. It’s creating a network for Zigbee and zwave non-Wi-Fi devices, while itself using your existing Wi-Fi network to get to the Internet.