The example you give is valid xᴇɴᴏɴ. The key and value may contain whitespace and must be delineated? <>s are that that made XML and HTML good.

So delineate them when they contain whitespace, for example "quotes serve exactly that purpose". There is no point in delineation when there is nothing to delineate, it's just needless verbosity in a language that aims to be "terse"

What exactly is good about <>s that you think it's the good in the bad XML?

There is a widespread agreement that XML is generally bad for the data serialization, while HTML is not much questioned as such. You can't carelessly adopt angle brackets without why such difference exists in the first place [1].

[1] Hint: "semi-structured data"

You mean ʜᴛᴍʟ is not used a such.

If you figured that out yourself, you should have also realized that angle brackets are generally considered bad for the data serialization. Cherry-picking my words without answering my whole point is not a good move.

> angle brackets are generally considered bad for the data serialization.

Not a point.