Well, the expression problem is a clearly formulated question: how can we have three desirable things at the same time (no need to modify existing code, no need for code repetition and no need for runtime type errors [1])? See also the project management triangle: if you need something fast, good and cheap, then fast, good and expensive won't be a satisfactory answer, no matter how many millionaires are satisfied with the latter.

[1] https://link.springer.com/chapter/10.1007/978-3-540-24851-4_...

Honestly, if you want to discuss the progress made on the expression problem by a dynamical language whose power and extensibility partly comes from a collection of informal, consensus based interfaces you have to start from a different theory.

Most people using language X are quite happy how X does things compared to languages they used before. That's why they use the language X. That's also the reason why I consider this type of argument unhelpful.

No, not "most people" and not "happy how X does things" but specifically people who have thought about the expression problem's opinion about how Julia alleviates the expression problem compared to other languages they know.