This WAS very true, and my stance for years. However like everything in IT....
" The only thing that stays the same, is NOTHING stays the same!! "
Enter MIMO, AC, and AX. 
Wi-fi (802.11ac/ax and above) with MIMO (multi in multi out) have gotten so fast that, with proper deployment, you can achieve faster speeds than Ethernet. I know, I know WTF, right!!
I have a client that gets near or over 1GB speeds via wireless from extenders using these. If you set them up with-in range of each other, and have a 1GB back-end like FiOS it's possible. I deploy it all the time, and have one next week. Don't get me wrong I use these only where I have too. I would rather Cat6 wired connections, then MoCA, then mesh, finally extenders, just saying you CAN.
for @boringzt622
My wife hates seeing wires. So at my desk I use a lowly Wi-fi AC (Asus AC66u) router, reconfigured as a "media changer" (part of the built-in config) to turn WI-Fi into wired connections. As you can see I get a connection of 866.7Mbps (between this AP-changer, and the main AP) but my FiOS is only 100Mb by choice so it's not an issue. Again if I wanted faster I could upgrade to AX.
I do the same for a food truck/restaurant I work with. They were told by their POS vendor that they could NOT sell off-site. Loving when people tell me what cannot be done, I made it happen over a mobile hot spot - media changer - Dell sonic-wall VPN appliance - 2 POS machine and 2 prep/make printers. Everything has worked 2 years running.
Waiting for the next thing that "cannot be done" 
EDIT: Note the RSSI: -28db If you are unsure what that means read this, or just stay under -50 (really it's above but lets not confuse things). Here is a Android app to measure. I have never found and iphone/ipad app that measure 802.11ac/ax RSSI if anyone knows of one please LMK
