ASCII is just a raw binary format. It isn't just for text.

The line endings problem really isn't a problem. Pretty much every text editor out there can handle different line endings.

I don’t think number nor date formats are relevant here. For example you could have that same problem entering text into MS Word. That’s really more of an issue if you want to use text as a database rather than a document format, which isn’t really something that even plain text advocates would generally recommend.

As for human language detection, that’s a much easier problem to solve than decoding a proprietary binary blob.

CSV definitely has its warts. But it’s not like that’s the only plain text option for serialising data. (JSON, jsonlines, YAML, XML, etc). Or you could use the actual ASCII codes reserved for records, if you really wanted something that didn’t require quoting and escaping in plain text. It’s actually a pity nobody does this.