I think the headcanon that Jon specifically doesn’t like Keats is a fanon thing (correct me if not), but there could be a good reason for that.

I mean, look at the way he writes:

“Bright star! would I were stedfast as thou art—
    Not in lone splendour hung aloft the night,
And watching, with eternal lids apart,
    Like Nature’s patient, sleepless Eremite,
The moving waters at their priestlike task
    Of pure ablution round earth’s human shores,” (from the eponymous poem)

Keats uses really high language (also this is from 200 years ago, but still. You can read Jane Austen easier than this.) Jon is obviously smart enough to parse this out, but he does not have the longest attention span. He doesn’t want to take the time to parse out what Keats is saying, thank you very much. It’s not worth it to him.