I used to be in the exact situation you are in today. Thinking my render images and skill levels were pretty good, yet still, I could not achieve the realism professionals would produce, which was frustrating.
So, I started to break down the render images systematically to understand where I was "losing the battle" with my render engine. What I realised is that you need 3 main components to create a high standard of realism. After a ton of research I came to the conclusion that for me to move forward I needed a little bit of help to get to the next level.
And so, over the years I registered for courses and bought eBooks related to rendering.
This helped me with my final step, and I now am able to create high quality realistic images just like the professionals I used to, and still, admire.
Today, I am excited to announce that my very own eBook is ready for release. All my experiences over the last 20+ years, the knowledge gained through multiple courses, and my education and daily project work are all combined into this eBook. Packaged up with all the knowledge in ONE place!