I used to suck at Messaging, and I don't claim to be a guru at it either even today. But let me elaborate:
At one point in my career, I would attempt to write a product one-pager (circa 2013-14) and my boss would redline the entire thing and hand it back to me.
I improved a bit. I learned to write about features as benefits, not about features themselves.
But I was still not stellar.
My work only increased by a step function when I took a step back and changed my approach.
I empathized intimately with a) the buyer persona's key problem b) the stage in the sales process where an asset will be used c) knowing my product's key differentiators (vs competition) like the back of my hand.
When I was sure about all the points above, messaging became easy.
The problem is not that messaging is hard.
The point is that good messaging is a consequence of knowing your product, its positioning, and your market cold.
Too many PMMs focus on copywriting, they may even write features as benefits -- but that isn't the same as understanding the "forest from the trees" and "knowing the terrain".