Optics technology is not advancing that fast. It had a rapid growth phase in the 17th and 18th centuries, and then a lot of the techniques remained almost unchanged until the mid-20th century, when the laser improved a lot of things. But consider that the big spectacular innovation of the last few years is Rayform, which patented a gradient-descent algorithm for making a makkyo mirror, as people have been doing for thousands of years.

There are some advances in, for example, using glass-ceramics instead of glasses, which give better strength, better rigidity, and enormously better fatigue tolerance. I don't think anybody makes multi-meter mirrors out of fused quartz, even though it would be a near-ideal material from a TCE perspective.