Wi-Fi is short

One possibility is interference. See this Apple support article—>Resolve Wi-Fi and Bluetooth issues caused by wireless interference - Apple Support. Unfortunately, the second most likely is a hardware failure, a broken antenna connection in the phone.

Have you tried on both the 2.6 GHz and 5 GHZ bands, to see if there is a difference?

There are a couple of software troubleshooting steps to try:

1. Go to Settings/Wi-Fi, tap on the i next to the network name and “forget this network”. Then try to connect again.
2. Go to Settings/General/Reset - Reset Network Settings. This will require re-entering all Wi-Fi passwords, but you won’t lose any content.

How close does it have to be? Normal range line of sight is about 50 feet. If there are walls in the path it will be less. And attenuation at 5 GHz is higher than at 2.6 Ghz.