Pretty standard for TV music at the time original series was produced, yep. Trek's (along with that for The Wild Wild West) might have been a little more emphatic than the average, but not by that much. This kind of music for TV shows continued though the 1970s without much change.
Composing style and influence did change in the bridge between the late 60s and into the 1970s, with many a composer moving toward less classical/symphonic scores, with some incorporating the then-experimental. If you listen to the work of Robert Colbert (
Dark Shadows,
The Night Stalker and every other Dan Curtis production), Andrew Kulberg (
Starsky and Hutch), Gil Mellé (
Rod Serling's Night Gallery), Billy Goldenberg (
Helter Skelter), Mundell Lowe (
Hawaii Five-O,
Attack on Terror: The FBI vs. the Ku Klux Klan, etc.), you would hear a wide range of different musical choices / influences not at all sounding like the "big Hollywood" / classical stylings of the various composers for TOS.
As you point out, it was somewhat subdued but still present in some early TNG eps -- however, definitely on the way out industry-wide in favor of music which remained unobtrusively in the background.
...more of a leaning in TV than film. The same year TNG made its debut (1987), on the big screen, you had some very motif-driven, "punctuated" scores such as Morricone's
The Untouchables, and a year later with Joe Jackson's
Tucker: The man and His Dream or Horner's
Willow.
TNG's Berman-mandated muzak instead of more noticeable, story-supportive cues was yet another indicator that he had no idea what made great Star Trek at all, and like most of the...stuff...in front of the cameras, the Berman-era music lacked any sort of heart, or purpose in being a character in the film. I could not imagine trying to listen to series soundtrack collections to TNG - ENT.
]I do wish TOS had more original scores recorded.
Have you listened to the complete soundtrack set?