Some elements of MASH's new reunion worked, while others were ultimately let-downs. The announcement that the legendary sitcom would ring the new year with a special was met with great enthusiasm for several reasons. For starters, the news came out of nowhere and was a welcome development, considering how beloved the series was. Secondly, it had been decades since the last MASH reunion, which took place back in 2002 for the show's 30th anniversary. Some of the cast had gathered in other venues, but there had been no official reunion since then. Finally, the Fox special aimed to celebrate the 40th anniversary of its finale, "Goodbye, Farewell, and Amen."
https://screenrant.com/mash-reunion-disappointing-great-reasons/