Christy Mathewson - Memorial Stadium was heavily renovated in about 1987-88. It is a nice place to watch a ball game and I disagree that it is "crumbling".

My vote for crumbling is old Palmer Stadium at Princeton between 1993 and 1996, when it closed. Sadly, the concrete (dating to 1914) was literally disintegrating back to sand. When it was torn down at the end of 1996, the demolition people had a very easy time - it came down and far quicker than anticipated.