I have seen discussions similar to this degenerate into personality attacks and slanging matches. Strong moderation is often required.
It seems that formal is formal and modernist is modernist and never the twain shall meet.

Part of the problem appears to be in defining the terms.

To my mind, formal poetry requires rhyme and/or metre to qualify. Not necessarily both - viz blank verse. But in any event, should have a discernible metre.

Free verse (should) have some kind of inherent rhythm but a lot of leeway is granted in this area. Assonance and near-rhyme often feature in the genre.

In the last generation or two, post-modernism has moved free-verse into the area of allusion and metaphor which in my opinion at least, puts it squarely in the area of intellectualism/esotericism at the expense of poetic expression.

Of course this is not always the case, and there is an abundance of very fine metaphorical work around.

My objection is when this genre descends into language-games. I've written a word-puzzle, and you have to work it out.
I, for one, don't have the time.

cheers
Peter E