While living in the Netherlands I never considered the wealth tax fair.
The government is making an assumption that I am going to invest my money and that I invest it well enough to get an average return. Not everyone will went to invest their wealth in risky assets though, and not everyone who does invest it will do well.
Their justification for the tax rate is only that, a justification. In reality the wealth tax isn't directly tied to investment returns and serves only to disincentivize saving your wealth. It pushes people to invest their wealth in risky assets, meaning they effectively want all individuals to hold a pile of IOUs rather than actual wealth accrued over their lifetime.
The same can be said for a target inflation rate of 2-3%. Adding a wealth tax on top just turns the screws a bit more, more strongly pushing individuals to put most wealth they accrue right back into the slot machine.