While Japan’s economic growth in the past two decades has not been staller relative to its own past in the 60s and 70s, it is not bad. The chart below, via Google, compares real GDP growth (year over year) with the US. [As an aside, Google provides on-the-fly graphs for search like “gdp growth of japan” and many others, like “life expectancy of japan.” See their public data page for more.]
If you plot the data of the G7 countries in the same chart, Japan does not look all the different from the others.
Source: World Bank, World Development Indicators [Google]