No, this is not true.
Central banks do 'create' money, but they trade it on the market for real assets.
The Fed creates dollars and exchanges them for an equal amount of US Tbills (bought at market rates). $1 created = $1 in Tbills on their balance sheet.
They're not just creating money and keeping it, or giving it away.
The practice of 'fractional lending' by retail/commercial banks amplifies this, but as far as central banks go - every dollar they 'create' is essentially backed by an asset that they keep on the books for that dollar.
The idea is to manage how much currency is in circulation at any given time, so that inflation (and employment) hover at certain target.
If politicians were 'printing money' to pay national debts, or buy stuff or whatever - that would be straight forward dilution.
What the Fed does is not dilution, and it's not a bad thing, it's a good thing.
Same for ECB.