For instance, they eventually stop calling Houlihan "Hot Lips" and start calling her Margaret because the nickname was demeaning or whatnot.

Hawkeye also goes into a fugue state and no one can reach him. It turns out that he was on a truck with Korean civilians going through hostile territory and there was a baby that wouldn't stop screaming, so the mother had to kill it (https://www.reddit.com/r/mash/comments/16fwy9m/what_exactly_was_wrong_with_hawkeye_in_mash/) to save everyone (https://www.reddit.com/r/TheWayWeWere/comments/ickin1/staff_at_a_norwegian_mash_korean_war_1952/) on the truck. Apparently, Alan Alda thought this was a searing episode (https://www.slashfilm.com/1425348/mash-episode-true-story-smothered-baby/).

Did the writers change? The show definitely was different.

That episode with the baby was the finale. Apparently that was based on several true occurrences where the mother smothered her baby to keep it from alerting the enemy. Anyway you slice it, that is a horrifying story.

I didn't like MASH for a very long time. Because I thought it was too preachy. It did get that way more so over time. Funny enough, the episode that actually got me interested in the show was that finale - not Hawkeye's story, but Winchester's, with the band of POWs he was conducting. After that I started binge watching several episodes a day (they reran it plenty in those days).