Cymbidiums need alot of water and fertilizer when they are growing. They also need lots of light to bloom. I think you might have identified a part of the problem: rarely watered and no fertilizer.
I don't grow Cyms much, but here's my
(just have one since they take up so much space) If that were my plant, I would unpot and check the roots. Anything that is firm is good, if it's mushy it's bad. If it had good roots, I think you should repot it in fresh medium, increase watering and add fertilizer. Depending on the amount of good roots, you may need to put it in a smaller pot for a while. If the backbulbs have any energy left in them, you should get some new growths. In the spring when frost is no longer a problem, you can put it outside and gradually put it in full sun. Bring it back in before first frost.
If it has no roots left, bringing it back to health will be very difficult but not entirely impossible.
Like I said, I'm no Cym expert, but checking the roots is definitely the first thing to do! Hopefully other members will be able to help you out as well.