Is your system engaging and satisfying? I am retired and listen about three hours a day and have to tear myself away each night. My system is the result of 50 years of research, effort, and investment.
A generality. Regardless of how good your system is, it can be significantly better when investing 2x in a component or the entire system. However, it cannot be blind investment… the investment must be in components that play to your tastes and compatible with your other components. To be able to do this, you must read extensively (and/or audition), I recommend professional reviews: Stereophile, The Absolute Sound, HiFi+. Read about your components… then others.
Given you cannot go out. After researching, try upgrading one component. What is the effect? If estatic… congratulations. Move on to the next.
Also, I agree with @mjcmt, musicality turns out to be the most satisfying parameter over time. The thing that emotionally involves you in the music. Many of us have moved to tubes in our old age, because they are musical.
If you haven’t read Robert Harley’s, the ultimate guide to High end Audio… it will point you in the right direction.
We could probably be of some help if you post photos of your system. Lots of time you can get greater sound just by moving things around, or upgrading a single component.