And though they may be too improv-based for your taste, you definitely shouldn't sleep on the live albums, especially the '64 tour with Dolphy. My favorite is "The Great Concert" but it's all gold.
And it makes sense that you'd dig Mingus because in general, he's one of the great jazz composers who was most influenced by classical music. But there's plenty of other jazz that's tighter and less improv-based that you may be able to appreciate, especially from the swing era (dixieland is fairly formulaic but still often mostly imp-based).
Duke Ellington is the most obvious example (FWIW he was Mingus's biggest influence). But my 2 other favorites from the swing era are Chick Webb and Artie Shaw and I think you'd probably be able to appreciate them. Chick simply had the tightest band around and the best arrangements (after Duke, who's in his own category) and also launched Ella Fitzgerald's career FWIW. As for Artie, he had a rich, sophisticated sound (and was also an incredible musician- definitely better than Benny Goodman IMO). Here's a few tracks: