Max download speed much less than plan

I was paying for 100 Mbps for a few years and the fastest I could ever get anything to download was 15 Mbps, so I upgraded to the 200 Mbps plan. That instantly brought the top download speed up to 30 Mbps, but that's still way less than I pay for. Every internet speed test says my download speed is over 200 Mbps, but when I'm downloading a file from any website and it's running at 30 Mbps my entire internet is essentially disabled until the download finishes because it's using all of the bandwidth. If I'm downloading multiple files the collective download speed never goes over 30 Mbps. I feel like this is probably a misunderstanding on my part of what those numbers actually mean. Is it common to only get 30 Mbps downloads with a 200 Mbps connection?