When you actually start to build a product, it's not simple as it initially seemed, am I right or wrong ?
Absolutely correct, on a globalized planet the likelihood of having a unique idea has decreased substantially, someone out there has thought of it in some form or fashion and it boils down to execution and healthy competition.
There's also the fact that the barrier to entry for businesses has increased substantially to the past. Many new channels to try and master, focus is very much key.
Additionally the "an easy business" concept doesn't really exist anymore either for the previous reasons and the fact that each business has its own set of complexities they're usually just trade offs in what the difficult part is. Scale? Initial capital? Technology? Sourcing? Logistics? etc
Tldr; Execution is everything
100%! I literally planned my daily tasks for the next year and yet actually completing them is a whole different story!
You are right, things can get complex quite quickly and also progress is always slower than you imagine, imho.