A key point that I had a hard time grasping when I first started my personal home studio, is that comparing a mastered professional mix to your own rough mixes is not really going to work. A professional mix/master has gone through many stages of production from much before an instrument is actually recorded.
What seems like sounds similar is not the same. I know that sounds vague and uninspiring, but it takes a long time to get the right tone recorded before anything you compare to will be similar. That does not mean you can't get close by any means. Just means you have to experiment and make the best of what you have. That is a positive motivation and it will work!
That I stated above, has a whole bunch to do with the instrument being recorded. How it sounds and whether it is possible to get the sound you want. Then there is the issue of recording environment, the player, the mic, acoustic room treatment, the use of software (gain staging/compression/eq)...
It takes a shit ton of time experimenting with what works, what get's you close, and what sounds like crap, before you have a grasp on what is really going on.
That being said, I have worked with many amp sims and high end Kemper and other simulation amps. Nothing ever beats a real guitar rig miced up. But then there is a whole big trial and error thing there getting the right guitar/pickups/amp/mic/room.
It took forever myself to learn that it is usually the simplest things that are the hardest to understand.
I used to have 3 different sets of used - under $500 a pair monitor speakers that taught me a lot. They taught me that they suck and I was mixing in circles. Once I purchased the ADAM A7x monitors, things just started making more sense. The monitors didn't solve the instrument/tone issues, but it made it clear what the issues were. More importantly IMO, is that there is no simple way to find out what works, what makes a great recording, or how to achieve it without finding out by trial and error. There is no simple answer. Time and experience makes things way easier. Oh, and a bunch of money getting the things in order to get to a higher level...
That does not mean you can't get close without spending a buttload of money. You just need to take the time to listen to what you have, and experiment with how to make it better.
Hope that didn't come across as me being a dick. That is just my honest opinion and what I have found that has been my voyage.