Perhaps the title of your thread should be 'Mixing critique" not criticism
Some good posts so far
First and foremost learning to mix is progressive lifelong process. Even the most successful engineers continue to learn with every mix. So don't get discouraged It is a big learning curve but IMO a very cool and enjoyable process
For suggestions: I listened in both headphones and on my laptop spks's
#1 Without monitors, even though it takes up a a lot of time, you might want to also do this constantly throughout the mixing process. Particularly every time you instantiate an effect or make a change in volume, and or panning . Get the plugin or change set up, get something you like then switch back and forth from the Head phones to your PC spk's . to see if what your doing in the HP's translates to Spk's
Because I agree with K vegas that there is a significant difference between listening on HP and on spks . For example the vocal seems ok in HPs but almost becomes (to my personal taste) distractingly, spread in the speakers. At least on my laptop. There are ultimately no hard and fast rules but just for reference, most lead vocals are panned in the middle. As are drums.
Couple of thoughts on general mixing theory and techniques.
The low end is where the most significant problems with mud occur.
This increases with each additional track, so while it may not a big deal with say a two track stereo guitar solo. It's a huge deal on the 100 plus tracks in a modern Pop song.
This problem can be addressed with subtractive EQ with both High pass filters and or cutting certain problem frequencies.
A couple of general rules of thumb (again not hard fast rules) are :
#1 first get the levels of each track balanced, with itself then balanced in the context of the mix. If your daw has a way to automate volume, this is a good use.( if not then ride the fader ) For example I dont know if the intro guitar part is the same track as that same ditty part later in the song, but its seems too low in volume compared to the rest of the guitar parts.
Again, it's a good general idea to get the volume and panning balanced first, on individual tracks and the mix as a whole, before adding effects.
You may later after adding effects tweek and change either or both (pan and volume) but for simplicity its a good place to start. Balance then go in and eq,comp, reverb , delay etc.
#2 cut the low end ( anywhere from say 250 hz or 160 hz on down) on guitars and vocals to leave more room and less mud for the bass and kick drum.
Also another common technique to clear away mud, is to do a narrow band cut on problem frq's from around 250 hz on up particularly around 500 hz on each track individually.
For this you have to have an EQ that is multi band and has an adjustment for the Q (the width of the frequency range being affected) so that you can make it very narrow and just affect the problem freq. area.
Hope this helps, But remember just keep making music and having fun. With time and effort your mixes will get better. Kev