It to a point depends on how much bandwidth you have. Netflix will have no effect say on someone with a 100mbps internet even watch 4k but someone with 15mbps it can cause issues.
What you describe happening now is how it should have worked before. Download attempt to use all the available bandwidth and they actually constantly push the limit to make sure they get it all. This will cause problems for games and many other things running. You normally need to artificially cap the maximum rate download run at. Normally you cap downloads at between 80-90% of your bandwidth depending on what else is running.
So either you are getting less bandwidth from your ISP now, check with speedtest or the download is running better. Things like steam are strange. Some time it will run at maximum rates and other it download at not even half the rate it could. Maybe the download site upgraded something and now it can use all your bandwidth.