Agreed, but that change was well underway before Charles arrived.
Initially the show resembled the movie -- 3 funny, irreverent guys (Hawkeye, Trapper, Henry) vs. two up-tight foils in Frank and Margaret, with very sharp, biting humor. Everyone else was in the background. They clearly decided to get away from that to appeal to a broader audience, so they drove off Trapper and Henry, turned Margaret into a more sympathetic character, and let Alda and his whiny sidekick Mike Farrell turn it into a preachy show. Once that happened, Frank's humor was wasted anyway.