But the complexity arises from wanting to make apps with something meant for simple documents. That being said, even building the simplest website nowadays requires a mind-boggling knowledge of the idiosyncrasies of the "languages".
I want to lose my job; I want the next best thing to be completely different but still allow for creativity and productivity.
Itβs reaping so much benefit that these experts can easily make mobile apps without learning another way to describe UI.
For me, the common places things break are, setting up a flexbox and not having the content scale to fit.
Trying to make an app like layout (so the page itself doesn't scroll though some content in various areas might) and again, trying to get various flexbox areas to either fit their content or get the content to fit its area without expanding the page past the window size (note: if you use overflow: hidden you failed)
In any case I'm not a UI/UX designer so I don't do it daily, therefore when I do need to do it it's always a bunch of frustrating trial and error.
That said, I do think there are a class of designers that also don't know these answers. They just know a few frameworks that handle all of this for them.
I get that, and that's why I declared it. I have two reasons why I think the opinion is still valid:
I'm not completely incompetent. I have produced useful web frontend work. After having spent more time on web technologies than a lot of others I still find it to be slower and harder. This point is about learning - I have done some learning in both and I can compare. It's a small sample size, but seems to agree with the experience of other people.
The other point is that most people talking about this are already experts in HTML/CSS. That learning is a sunk cost for them so they're not making fair comparisons. I also sometimes feel like there's a little 'Stockholm syndrome' - they've invested time and effort in learning the techniques and tools required to produce good quality web UI, and now that they can they overlook the effort required to get to that point and proclaim the wonderful nature of what they're using.
The sunk cost thing is the important aspect. I'm not even saying that it's wrong that it's become the standard UI description language - it as at least an open specified standard. I'm just saying that not enough attention is paid to the downsides.