These are interesting observations, and also reflect a trend I believe a lot of long running shows/franchises ultimately evolve, mainly that the narrative focus changes from situational ("What will our heroes encounter this week?"), to character based ("How does what they encounter personally affect them?"). Coupled with serialization, that leads to The Soap Opera Effect™. The Trek movies certainly show signs of this by comparison to the series, and TNG onwards made it a hallmark of the franchise's storytelling (perhaps only TNG's first few seasons balance that out more between actually growing the characters and having action-adventure plots).
It was most striking to me in 2005 when the modern incarnation of Doctor Who premiered, and my most immediate impression of the storytelling style shift was that the older series was about Adventures In Time and Space, the Doctor and his friends landing in a new situation every story and sorting it all out without developing a personal attachment or involvement, whereas all of the stories in the modern incarnation had to have some kind of personal stake or growth for the main characters, or most particularly, a roster of semi-regular family members to tie the characters into that.
Not saying one style is particularly better than another, but they are different approaches to writing a narrative.