I think its really hard to say whether the 2010s have been particularly better than other decades because practically I've only been exposed to new theatre in this decade. But there have been some very incredible plays. The Ferryman, Choir Boy, What the Constitution Means to Me, Indecent, Curious Incident, The Wolves, White Noise, Sweat, The Flick, Slave Play, Daddy, Venus in Fur, Between Riverside and Crazy, Father Comes Home From the Wars, Disgraced, The Humans, Vania and Sonya and Masha and Spike, King Charles III, Clybourne Park, Constellations, Fairview, Dance Nation, Other Desert Cities, Bengal Tiger at the Baghdad Zoo.
I mean that's a pretty impressive list and those are really just the ones off the top of my head. I will say, on the flip side, the 2010s have been a pretty awful decade for musical theatre. Outside of some select gems (Great Comet, Hamilton, Fun Home, Hadestown, Once, The Band's Visit, etc), the average musical has definitely tanked tremendously. Musicals are playing it safe, and plays are taking the forefront due to their risk-taking.