This is at least partly true. Several architecturally soulless, cookie-cutter, multi-purpose stadiums–many of which were too big for baseball–were built in the 20th century and there was a spate of construction starting in the early '80s to replace them, not only to put in luxury amenities, but to also be more cozy and attractive for fans.
The new stadiums tended to reflect “traditional” architecture, as opposed to the concrete doughnuts that were largely replaced by smaller, single-sport venues.
Most of the older stadiums were bland and ugly and undistinguished/indistinguishable architecturally and largely aren’t missed.–
Atlanta-Fulton County Stadium, 1965, replaced by Turner Field in 1996
Baltimore Memorial Stadium, 1922, replaced by Oriole Park at Camden Yards in 1998
Bloomington Metropolitan Stadium, 1956, replaced by the Hubert H. Humphrey Metrodome in 1982, in turn replaced by Target Field in 2010
Cincinnati Riverfront Stadium, 1970, replaced by the Great American Ballpark in 2002
Cleveland Municipal Stadium, 1932, replaced by Jacobs Field in 1993
Denver Mile High Stadium, 1948, replaced by Coors Field in 1995
Houston Astrodome, 1965, replaced by Minute Maid Park in 2000
Milwaukee County Stadium, 1953, replaced by Miller Park in 2001
Philadelphia Veterans Stadium, 1971, replaced by Citizens Bank Park in 2004
Pittsburgh Three Rivers Stadium, 1970, replaced by PNC Park in 2001
Queens Shea Stadium, 1964, replaced by Citi Field in 2009
St. Louis Busch Memorial Stadium, 1966, replaced by another Busch Stadium in 2006
San Francisco Candlestick Park, 1960, replaced by AT&T Park in 2000
Seattle Kingdome, 1976, replaced by Safeco Field in 1999
Washington Robert F. Kennedy Memorial Stadium, 1961, replaced by Nationals Park in 2008
– The fact that Kauffman Stadium in Kansas City (1973) is attractive and still well-liked by fans makes it a notable exception.