Many people don’t quarantine and are okay. Despite what may be said, it’s a matter of blind luck, all it takes is one sick fish. Best way to increase your chances of success is buying from reputable vendors like dr. Reef or TSM which quarantines their fish. Avoid liveaquaria and petco at all costs.
Qt is as simple as a 10 gallon tank with some pvc pipes, a hob filter, and a heater. You won’t regret it if you do. I didn’t quarantine my first batch of fish and lost them all, so I will always advocate for qt.