It's so bad in SharePoint. I try to avoid !important as much as possible, but it's really hard. Maybe it'll get better with the release of the SP Framework. Who knows?
But I'm okay with it either way. We'll still have to help people figure out where master pages / page layouts still fit in, and we will (hopefully) have an easier-to-reason-about path to use React or whatever other framework with SP in a supported way.