DS9 VGR and ENT were the only shows to use CGI and even then DS9 and VGR mostly used models
DS9 didn't begin to use CG until around halfway through the series (I'm talking for hero ships mainly)
Not entirely true. A very crude CGI model of the Enteprise was used in "The Ensigns of Command" when the Enterprise is up against a Shelliak ship, the alien space-baby "Junior" was CGI, there's a shot in "Masks" of the Enterprise vaporizing an asteroid with a hidden artifact in it that's CGI and most of the time when we see people in the "empty" holodeck the holodeck grid-room is CGI. (IIRC. they has smaller holodeck "room" in practical but they also at times used CGI to represent a much larger, and vaster, holodeck room.
Now, granted, they didn't use a *lot* of CGI. But they did use some.
But, yes, the vast majoirty of SFX ship shots were practical using models. The Enterpise had a Six-Foot and Four-Foot model that were used (and I believe even at times a small Two-Foot model) for SFX shots. It was sturdily mounted on likely a steel pole and was mostly stationairy. I don't think any legit production outside of Ed Wood movies or other horrendously low-budget movies from the early eras of film used "models on strings."