The problem is not that the X-type is a rubbish car, because it isn't, in fact in many ways it's very good. The problem is that it isn't a proper Jaguar. As capable as the Mondeo platform is, it's still a Mondeo platform - i.e not a Jaguar platform.
What actual difference does this make, though? And if we are to beleive Jonnycoupe it seems the Mondeo is built on the X-Type platform and not the other way round anyway...
Platform aside, Jaguar should never have entered this market in the first place. Ford, in its infinite wisdom, decided that Jag should become a mass market manufacturer - this meant producing a 3 Series/A4/C Class rival. Jaguar are a luxury brand and entering this market only served to damage this 'luxury' image.
Had the car not been harnessed with this ridiculous 'poor mans not a proper Jaguar' image I suspect it'd have done very well. Mercedes Benz are a luxury manufacturer as well - infact many beleive Mercedes make the worlds finest luxury cars this side of Bentley and friends - yet this didn't stop them entering the very same market in 1986 with the 190E. Nobody called the 190E a poor mans Mercedes. It was a great success and so too was the C Class which followed it. Infact in terms of actual product the W202 C Class was frankly a rubbish car - yet it didn't suffer in the way the X-Type, objectively a better car comparatively speaking, did.
Nowdays the C Class makes up the bulk of Mercedes Benz sales volume. Jaguar saw this path as one they rightly wanted to go down with the X-Type. It was, however, ruined by 'image' not neccesarily poor product.
Jaguar have since admitted this and as a result the X-type isn't being replaced. Instead, Jag are focusing on producing proper, British, world beating luxury cars. Now, in the post-Ford era, they're no longer trying to compete with the Germans in terms of sales, because that isn't what Jag is about.
I think whats really happened is they've admitted they are incapable of competing not that they dont WANT to compete. It's not what they are about but it should be - after all, a company exists to increase shareholder value not to provide men in smoking jackets with something to discuss at the local public house.
I certainly wont be mourning it
Given you were 9 years old when the X-Type appeared I'm not entirely sure that whistfully dreaming of the Jaguar of old is really that relevent for you (or me!).