An old Chinese proverb says:"The best time to plant a tree was 20 years ago. The second best time is now." The time to start developing your software product was probably 15 to 20 years ago, when Amazon, Google and many others were starting. The second best time is as soon as possible.
A long a$$ time ago I created a simple React component that would lazily load an image and while it’s busy loading an image it would show a placeholder and wrote a tutorial how I did it. It is inspired by Polymer’s iron-image and a neat little trick how to transition from placeholder to loaded image.