I had no problem learning it. But I was taught to read using a phonetic method, so I’ve been decoding sound symbols since I was a preschooler. I noticed that some people had real difficulty learning IPA in my linguistics and foreign language classes. I wonder if it is because they were taught to read using a “whole word” or “see-and-say” method?
If you can learn the old dictionary symbols, then you can learn IPA, or at least the IPA symbols for English sounds. Just look at the examples given in the key.
Here is one tip that might help you. English “long vowels” are actually diphthongs in the most widely-spoken dialects—two vowel sounds merged, or a vowel and a semi-vowel, like the ‘oy’ in boy or the ‘ow’ in howl—and IPA represents them as such, using two symbols to represent them, instead of the one symbol that you find in the traditional dictionary system. This might be confusing if you are used to thinking of them as single sounds, but again, just look at the examples in the key.
You can learn the Greek and Russian alphabets too, if you care to. This stuff ain’t rocket science. Think positive.