I've tried this numerous times, and even tried different tutorials from the one provided on this site(https://www.arduino.cc/en/Tutorial/HelloWorld), and none of them have worked, all giving me these squares for some reason. That said, I'm sure that I'm repeatedly making the same stupid mistake but cannot find it. If anyone can spot it, please let me know as I genuinely have no idea what I'm doing wrong here. And apologies for the same colored wire.
Your photo shows (in addition to a lot of yellow wires) a header strip with no display. This implies that you are
simply placing the display module on top of the bare header pins.
This will not work as you have already seen. You MUST solder the header pins to your LCD module.
Where did you get all those wires of the same colour?
Without the display being there, it is amazing it even shows "squares".
Seriously, it is a basic point of electronics that you have to actually connect things together so unless you have a female socket header strip already soldered to your display, then it is not going to work at all reliably.
I am pleased to see you have not got a potentiometer connected to Vcc. A 220 Ohm resistor on pin 3 should be just about right for contrast. If R8 on your display reads "101" or 100 Ohms, then you do not need the 229 Ohm resistor in series with pin 15 - unless you think the backlight is too bright.