No, that's been a common proposal from economists pretty much since people started examining how economies work. Some places do have a capital gains tax of zero. Switzerland is one of them, and Switzerland is economically more successful than the rest of Europe.

Tax is one of those issues where there are actually correct and incorrect answers, thanks to many hundreds of years of active experimentation and relatively simple/robust theory. But people ignore the correct answers for social reasons.

The correct answer on tax is:

1. Figure out how much money the state needs to supply the services that are in-scope for it to an acceptable level of quality.

2. Aim to raise that much in taxes.

3. Optimize deadweight costs. That is, configure taxes to minimize the level to which the activities being taxed are discouraged and driven either out of existence or abroad.

If you do this sort of thing then you get Georgeism, you get zero capital gains, I think you get zero taxes on businesses, and a bunch of other policies I can't remember right now. The results can be economically very efficient i.e. they make everyone better off. However, almost nowhere uses them because there's nothing in the above three items about social engineering, and governments use taxation largely as a tool of social engineering. And in particular to please leftist voters who use the tax system to penalize wealth for its own sake, and to reward groups of client voters. Many governments also have a lot of trouble defining what's in scope for them and then working backwards to needed tax revenues; they prefer to raise as much tax as they can manage without totally crushing their economies and then find ways to spend it.

If their argument were true we should set them as far negative as possible - we should tax 100% of labour and give all that money to capital owners. Which is kind of something that's already happening.