Which is one of the most important rules for cryptocurrency to be successful

I think the opposite. I believe that networks that do not manage inflation well will forever be volatile and difficult to stabilize. The only way to create a good currency is to stabilize the value of tokens with proper management of the inflation rate. Any token with a supply cap can't accomplish this by design.

Inflation has been thought of as a bad thing for quite a while now, but eliminating inflation is not important: all that matters is who controls the inflation. With crypto: stakeholders control the inflation, so comparing that to a central bank is impossible.