I agree? My favourite poem has barely any rhymes. And the AI actually manages rhymes fairly often ("If a man be true and of humble heart / Then none can deny him his rightful part / Love will lead him through the dark of night / And show him the truth that lies before his sight" is AI).

But that's not why poems were easier. It tends to be far easier to identify a poet's style from a brief snippet, and the AI has some trouble even keeping to a consistent metre, let alone riffing on it in a sensible way. Some modern poetry might not bother with metre at all, but that wasn't really a thing for Byron and Wordsworth, and it definitely wasn't for Shakespeare.

Also, every word of a really good poem is usually carefully chosen, because a word out of place stands out like a dropped note in a song. Whereas you can have passages that seem fairly out of place in a novel without overly damaging the overall work. Partly because prose focuses more than poetry on the meanings of the words, and far less on the sound of them. And partly because poetry just tends to be shorter.

You can identify a lot of the AI poetry by reading it aloud and realising it just doesn't sound good. At all.

Likewise, the ideas in the poetry are easier to judge. A passage from a book might tell us 'It was 13 O'clock in April', whereas a poem might tell us that 'April is the cruelest month, it mixes memory and desire'. The AI seems reasonably capable of imitating the factual kind of statement, but less capable of meaningfully dealing with more abstract value judgements. And when it tries you get things like "Through the darkness I forge, To a life I must endure, For this is my journey, My heart must be sure."

Even aside from the fact that it sounds bad, that is the kind of deep meaning I'd expect from a song written by a 13 year old emo whose parents just don't understand. Not Lord Byron.