You don’t have a case of “shit ears” but a case of shit room. As Gary_W pointed out your room is nearly square. I’m not sure what heoght your ceiling is but if it is also at a “bad” ratio the sound in your room could be really terrible. In a room that size your listening position could be very close to the dead centre of the room which is also the absolute worst place to be listening. Very small changes to your listening position can make a massive difference to the sound you hear in a room like that. To experience this try running a test tone generator (most DAWs have one built in) startng at very low frequencies and gradually increasing this. With each selected frequency move around the room and notice just how much the perceived volume changes.
Definitely don’t waste your money on expensive new monitors or other gear until you have dne some basic acoustic treatment. Rockwool (or OC703 if you ar in the Us) is your friend and is relatvely inexpensive. Unfortunately, in a room that soze with those proportions you will never be able able to get the bass properly tamed as their isn’t enough space for all the treatment you would need. However, you can still make significant improvement for relatively little money. Fortunately, with guitar you aren’t overly concerned with super low sub bass frequencies anyway.
Just be aware that you will need quite a lot of Rockwool and the positioning of it is important. Start with corners including where floors and ceilings meeting walls as they have the biggest impact. Just be careful not to cover every reflective surface as totally dead sounding rooms are also a very unpleasant environment.
If you can’t tame the room then using good headphones will be a better option than upgrading your monitors.