Most web developers should be more concerned with performance than they are. In the wild, on a fairly recent MacBook Pro, I frequently run into sites where I deal with 100ms+ input lag. And every time I check, it’s always React (sometimes Angular) under the hood. These are sites with great dev teams too. Stripe, Airbnb, Squarespace to name a few, suffer from severe performance problems on modern hardware. And those issues stem more from the diffing and reconciling stages than the actual DOM itself, whose updates are minimal for things like entering text into an input.