The old rules were if you held an investment for over 12 months, when you sold it you only had to pay tax on 50% of the gains. So if you bought $1k of shares and they went up in value after 12 months to $2k, you would only have to pay tax on $500.
Now, you will have to pay a minimum of 30% tax on the whole $1000 gain. That means you have to pay a minimum of $300 in tax on that $1000 gain, whereas before you might have had to pay 30% of $500, which is $150, so you’re basically 50% worse off now.
This affects everyone, not just the rich. It makes investing in anything in Australia much riskier and less enticing. Taking a lot of risk only for the government to potentially take half of your reward is disgusting. They don’t refund you 50% if your investment goes to $0.
Tl;dr - the issue is that the government is now going to steal even more of your hard earned money, so it will be even harder for anyone to get ahead.