Jerry may have had several other gigs to do at the time, and might not have been available for Generations. His last Trek movie before First Contact was Final Frontier. He was rather intermittent with the first few Trek films. (TMP, TFF, and then returning for all the TNG films after Generations).
On another note, methinks that the producers were out to simply show how well TNG could measure up to the big screen with largely television generated effects....and the music.
Well...they got what they wanted....and what they got was a two hour episode that just happened to transpire on the big screen. A big screen movie with broadcast level effects.
There was really nothing big screen about Generations (or next two follow ups). Even the saucer crash filled up the screen better on a TV than it did in the theater.