In 5 years we're gonna wonder how we got to the point where you can't easily turn off wifi, slowly dumbing down devices for all of us for the sake of your project manager and the like.
On my 6+, the sequence is: press home button, tap Settings, Wi-Fi, Off. That's 3-4 depending on whether you count the home button.
On a 6s or newer, with 3D touch, you can cut it down to 2-3: unlock, force touch on Settings and toggle WiFi from the menu that appears. (That might be 1-2, I forget whether you can force touch and drag to what you want to activate, or whether it has to be a separate tap.)
I didn't know about using force touch on the settings app. However when I tap on the wifi menu entry that appears, I still need yet another tap to disable wifi.
Anyway, here's my count:
1. use touch-id to unlock the phone
2. press home to get to first screen with the settings app (if you aren't already)
3. tap Wifi
4. turn it off
You then need to navigate back to where you were previously.
The problem isn't that Apple made it hard to turn off WiFi, it's that they changed one of the controls without making it clear that it had changed.