David Bell is actually a very good composer, but like all film/TV composers, he was hired to do what the producer (or director, in film) asked him to do. If you listen to his scores for other shows, they're a lot richer than what he did for ST. He did really good work for Murder, She Wrote
and the short-lived Hal Linden/Harry Morgan mystery series Blacke's Magic
. (He also did shows like Simon & Simon
and In the Heat of the Night
, but I didn't watch those.) My father (who was a radio announcer/programmer for our local classical station) actually interviewed Bell once, back in the '80s before he became a Trek composer. I was already a fan of his at the time, so I was rather impressed.
And while I'll agree that Bell's wallpaper scores tended to be among the most repetitive, he did really good work in those Trek episodes where he was allowed to move beyond the "wallpaper" paradigm, like the weird "carnival" music in "The Thaw," the beautiful alien source music in "Remember," and the superb Captain Proton
scoring he did in "Bride of Chaotica!" I also really enjoyed his comedic work in DS9 episodes like "Take Me Out to the Holosuite," and his score for ENT: "Dear Doctor" is really quite impressive.
As for Baillargeon, all I can say is that I've always rather liked the sound of his music. No, it's not very melodic, but it's got a distinctive style that I enjoy. I don't find it wallpapery at all. I particularly like his scores to ENT: "Vox Sola" and "Rogue Planet," the latter of which is quite lovely.