Hi Justine!
I really love the push for CSS grid in concert with flexbox. That spec seems very promising and will solve a lot of layout issues on the web. In general, there's also been an increasing awareness of CSS performance in terms of building pattern libraries and delivering streamlined code to engineers and team members. That's a great trend I'm seeing!
I think some of the "worst" trends are a little tangential to me from CSS -- everyone is using the same typefaces on every website! (Hello "Open Sans"). And also not considering accessibility when adding style (like color contrast and adding descriptions to elements that have images included as backgrounds)