For me it's probably substandard recording/monitoring gear. Everything I record seems to sound "off" in some way that I can't put my finger on.
preface: sorry for the novel
Stereogram! I can relate sooo much. I found what for me seems to be a workaround for the time being. I used AKG K44s for a long time because they are cheap and my at local Guitar Center. Unfortunately the cans on those don't work for me. They are too tight and it severely limited my sessions. I upgraded, if you want to call it that lol, and now have AKG K52s. They're not bad at all, however after about six months though I felt the same as you and startied a vein-less "my sound" deep dive. I don't have monitors at all and am using a sub par laptop as it is so I felt there was something I could do to help my issue.
As it turns out I learned about the flatness levels of different headphones. This led me to finding a scholarly article containing the results from a scientific test of different headphone monitors. They also had a frequency graph where they perceived how the K52s specifically colored the signal. I took this to FL Studio and slapped Voxengo's Marvel GEQ into mixer track one and compensated where the frequency response appeared to boost and cut respectively on the graph.
From there I fleshed out a little mix to test my theory.
I routed everything to it's own mixer track and routed everything to track one before going to the master. I started playing with the wet/dry knob on the GEQ's assigned effect slot and brought down the higher frequencies in the GEQ just a tiny bit. It felt like there was so much more room in the mix in my opinion.
And that's just it, music is about taste and preference.
I exported the mix with D16's Frontier from CM mag and took it to the car. It sounded pretty darn good there too. I also ran my mix through SPAN and if I understand the user manual and the meters correctly, my mix thus far stays +1 on the correlation meter (mono?).
Of course we all know a mix takes a heck of a lot more than that, and but another thing that makes me feel like my sound is "getting better" is just coming from what sounds good to me, the music I listen to that isn't part of what I'm trying to create and the mood I'm in. Luckily I have loved music for a long time and have been a musician for almost as long and that is making it easier make my sound and not find it.
Dude, if I can find that article I will come back and link it, maybe you can find something useful or at least have an example of something to look for relating to your gear you know? I just wanted to share this while it was hot in my brain
Hopefully this helps you out bro!
B
edit: FOUND IT! the website is called reference-audio-analyzer.com and because my post count is too low I am unable to post links. PM for link to specific page I referenced if desired.