Bitcoin cant replace money. Money is supposed to be spent and not hoarded. Thats why inflation is needed so people go spend their money and create jobs and wealth for society as a whole.
Why do people believe this? Where did you first hear it?
This is my personal opinion Everyone gets upset about inflation, its like this bad word.
Money itself is a means of exchange, a substitute for trading actual goods and services. It doesnt need inherent value, it only needs to be accepted by society.
If the growth of money is limited and money over time increased value people are less inclined to spend it. If its going to be 3% worth less next year people will go out and spend it for example for gold.
Now the money beeing controlled and monopolized by a central authority is an entirely different problem.
Check out The Wörgl Experiment for evidence how money circulation creates wealth and not money hoarding/saving. You can save in real estate and commodities but not in money. You can trade in commodities like gold but theyre not good money for society as a whole.