When the Netgear was working 100%, was coverage and performance sufficient? If so, I’d get another.
How extensive is your Ethernet? Could you get it to every room? A mistake I often see is people who have homes with interior walls that block WiFi, and think mesh is the answer, only to discover that they cannot get the mesh units to connect. IME mesh is more but lower power WiFi units (with awareness of their topology) as opposed to a single higher power device.
From your description, for mesh, I’d look to have an Ethernet backhaul, with enough mesh units to give consistent coverage through the apartment. Don’t overdo it though otherwise devices will be transitioning between APs more than they need to.
I have always had problems with Wi-Fi in our house. I’ve tried DLAN (Ethernet over power cables), Wi-Fi and other solutions, but couldn’t really get decent performance.
I have now put in a Ubiquiti Unifi mesh network, this is giving me a “good” 100mbps-120mbps over 802.11ac between my cellar, where my office and the main network switch is and the bedrooms on the 1st floor (2nd floor in USA-speak). My previous Fritz!Repeater mesh (Fritz!Box 7490 + Fritz!Repeater 3000) managed 50mbps to 90mbps over 802.11ac, over a distance of 11M. Part of the problem is, like you, the floors here are reinforced concrete.
But the DLAN dropped to under 50mbps back to my router, luckily my internet connection is only 50mbps at the moment. It used to top out at 100mbps (a 1.2gbps adapter), but a new device somewhere seems to be causing interference.
Therefore I am looking to run Cat.6 from the router, which is by the front door, down into the cellar and a second cable from the access point to the cellar.
Since the OP mentioned being in an apartment building, the issue may be that the surrounding “neighbours” have added more wireless gear and their new gear is leaking its signals into the OP’s collision domain. If that is the case, mesh might help more than one new all powerful central router.
True. All the routers I’ve ever used have automatically adjusted the channel to take this into account and we’ve never had that many near-by Wi-Fi access points to make much of a difference. At work, there are 2 other APs in the area and at home about 3 in range on most days, when the weather is “just right”, we get about 5.
What might be worse is if you have partial channel overlap with a neighbouring transmitter. If I understand it correctly, wifi systems cope quite well with being on the exact same channel as each other, but less well with being in the “overspill” area of an adjacent transmitter. For example, in the 2.4GHz band transmitters work best if everyone uses only channels 1, 6 or 11 - that way, there’s no interference from overlapping channels. WiFi Analyzer gives a very good visualisation of that overspill on its display.
I’d welcome correction from anyone with more technical knowledge if I’ve stated anything incorrectly.