I don't agree it is continually, I see Chrome as already in the 'extinguish' phase. Chrome was able to make the improvements faster than competitors because - without an bottomless money engine in the form of a search monopoly - they weren't competitors at all. The price we pay for a few years of higher performance may be many more years of reduced innovation from competition.

What giant leaps? WebP images? AMP pages?

Chrome won the browser wars a decade ago, it hasn't done anything since except try to track and monetize that audience.