There is much to do with the room you are in as well. $2000 studio monitors may not be the best decision if the space isn't helping you.
Let me try to place this in perspective here: I have been mixing in shitty rooms for decades. It is possible that I can pull shit out of my ass because of that experience from shit monitors, because I have been there before. That obviously is not the best way. Lot of second guessing and learning from those guesses.
Once I payed attention more about the room I am in treated it acoustically, and invested in better monitors, it got way easier. Could I do that as easily with crappy monitoring? No.
Did room treatment make a huge difference with the ease of what I was hearing? Absolutely the most beneficial and least expensive investment. Would it be the best investment if I didn't upgrade my monitor speaker? Hard to say.
So it really depends upon your budget and your goals. Both monitor speakers and the room they are in are huge factors that will work together. If one of those in a budget were to be my first investment, it would be monitors at first. . But the close second is the cheaper room treatment. But then, that is going to depend on the room. If you have a square box of a room, you are going to struggle with room modes. It is just a consequence of where you are. Better monitors will help, but the elephant of the room will still give you struggles.
Look up Room Modes. JH Brandt has a calculator that will show you what you are dealing with. My control room in it's present state with DIY acoustic treatment has a huge null at 80hz. Meaning that frequency is cancelled out no matter what I do. So I am changing the size of the room. Granted, not everyone can do this. Do I still create quality projects with this lacking frequency? Yes I do, because time and experience has allowed me to learn how to compensate. I could not do that easily without good monitors, a sub, and the room treatment to attempt to control it.
Sorry if this is beyond what you were looking for man. You can create great music in any room. How easy and well that is done, really just depends on the guy writing and recording. Great recordings have been done in shit spaces with crap gear for decades. It really comes down to you man.