Only those with a lot of debt claim it’s not a bad thing. It’s not a bad thing only if you have no intent of ever paying it off.
And those self made millionaires who use leverage to build businesses and purchase real estate. Just an example is an average Joe engineer I know who currently has a 3 million net worth. He has 6 million in high appreciating assets and 3 million in very low interest debt.
For 20 years, he used his salary to purchase appreciating assets (US stock index funds and real estate) and took out low interest loans to purchase more appreciating assets and start a business. He quit his engineering job to run his real estate business because it now pays more than his engineering job and it's a lot less work and stress for him.
