Ohhh! That is unfortunate.
As an original story progressing like a detective investigation, and as a setup for the following games, the original ME is IMHO, a work of art. Superb pace, great dialogues, great characters, great dilemmas and revelations, enticing main missions and involving surroundings sprinkled with great music. It is, for me, the best iteration of the franchise. And, together with Dragon Age Origins, the last really great game from Bioware. The 2 swan songs that still had the Baldur's Gate/KOTOR series' DNA.
The story, character emotions and dialogues displayed, began a long smooth decline with ME2 and tumbled badly in ME3. A consequence of ME's original owners and creators leaving the studio after Electronic Arts's purchase of Bioware the year ME1 was launched (2007). That decline continued inexorably until today, when we see the pale shadow of the great studio that Bioware once was.
All, as usual, a consequence of the evil bean-counter empire that is EA.
If you do, please play it from the beginning and fully explore all stories and dialogues possible (multiple plays are necessary). They are, specially the first one, really great "modern" games with most of the cause & consequence typical of the older great RPGs (well, ME3 probably isn't...

).
I understand. I might update you on its validity as an expansion, when I get the chance to experience more about Odyssey gameplay.