Better than complaining
You can complain that your Product Manager asks for the impossible.
You can complain that your boss changes his mind every day.
Or you can start explaining.
Explain to your boss how changing his mind every day is hurting his company.
Explain to your Product Manager that there are more standard ways of doing things faster and better.
Make it your problem to solve your company’s problem.
After all, that’s what you get paid for.