Pretty much all syntax is unreadable if you don't know the lingo. For example, try presenting the ubiquitous

    for (int i = 0; i < 10; i++) {}

to ten random people without prior programming experience and see how many of them can correctly tell you what all that means. Similarly,

    { a, b in a > b }

is probably not very clear to people who don't write Swift and perfectly lovely closure syntax to people who do.

There's language syntax that's actually unreadable, for instance due to using names that obscure or otherwise don't clearly express what a construct is/does or using the same operator/keyword for too many different context-dependent purposes. I don't quite think the sheer presence of angle brackets makes code unreadable, any more than the sheer presence of curly braces or parentheses do.

That isn't even close to valid C++.