That's such a common one! It's even worse that there's a chocolate bar in the UK called "Turkish Delight" which is nothing like the proper "Lokum". It's not very pleasant :)
Turkish delight (not Cadbury's chocolate bar) is delicious.
The chocolate bar is just crap mass-produced Turkish delight wrapped in chocolate. I agree it's not very pleasant, but I don't know what else one could expect.
It's not that real-world Turkish delight is bad, per se, so much as that Lewis makes it sound so life-changingly incredible that the real-world version is bound to disappoint by comparison.
On the one hand, it was mind-numbingly delicious because of the White Witch's magic making it incredibly addictive, rather than simply the virtue of being Turkish delight.
But why the choice of Turkish delight? A combination of status-signalling and unavailability [1] (post-WW2 sugar-rationing was still in effect when the book was written).
