Never mind what you used to have. What kind of bike do you want to buy? What do you want it to weigh?

Components don't affect the ride very much at all. Mostly it's the fit, the tires, and the weight. Geometry plays into it, too. While the frame is the most expensive part of the bike, the most important upgrade is tires, not the frame. Components are the least important thing.

If the Fuji originally came with Ultegra and now has Tiagra, maybe the seller downgraded it. Or maybe he started with just the frame and built the bike that way. It makes the bike worth a little less in market value, but it doesn't affect ride quality.