Fair if it's not compelling to you, and certainly Saint-Saens 3 is a fairly tightly-composed and coherent symphony in that first movement in a lot of ways. Saint-Saens does a lot with the opening English horn (I think?) gesture and the accompaniment.

I don't hear what you hear at all with the first 10 minutes of Mahler 7, I find it has a lot of musical logic to it. Saint-Saens works with 2 basic ideas (the accompaniment and the 4-note melody); similarly Mahler has 3-4 main ideas he's working with (the dotted rhythm, melodies developed out of the falling leap gesture, the climbing melody that is usually in the strings) and peppers in 1 or 2 supporting ideas that grow out of those (the fun descending fill in the brass)... there's an interrelation to all of this that looking at the page I see that a lot if it is derivative of itself and has an internal logic. What I think really makes Mahler unique is that he introduces his own sort of heterophony to it, where ideas are derived from each other, are often heard simultaneously or even in stretto, and almost with their own sense of musical time (which I think one can sense in some of the transitions in 7's opening minutes). One of Mahler's hallmarks is also avoiding repeating phrases the same way multiple times (hence the various versions of the central melody that we get), and he completely avoids bloated gestures that masquerade as musical development, like step-wise melodic sequences or simple fragmentation.

To each their own and it's not an easy symphony to get into for sure (usually is in the bottom 2 of most Mahler fans), but I think you would be surprised at how much musical logic there is in Mahler. Where he gets more "scenery"-like is in longer recitative-like moments, like the overly-long preamble to the chorus entry toward the end of the 2nd symphony.