That’s just so wrong. Line heights, line lengths, fonts, font sizes and margins are vitally import visual properties of your website. If you want to make sure that you picked the correct values for those properties and if you don’t yet have copy, you should use Lorem Ipsum. Text is certainly not just a visual element but it is also a visual element.The important point is that lorem ipsum is not content, rather, it is a tool for approximating the aesthetic of content that might be placed there in the future.
Nobody is saying that design begins with fonts/layout/color (although that does happen at times), rather, that when you get to a point where you need to decide how bodies of text will look, you use things like lorem ipsum to approximate how other text will behave within that field.
The other thing about lorem ipsum, which you may be missing and the op certainly misses, is that by not actually being english, you don't get hung up on the meaning of the content, rather, you can pseudo-objectively evaluate the aesthetic choices used to set the text. again, the whole point is to create a template for setting actual text very well.
the largest problem with lorem ipsum is people using it who don't understand why they are using it. I think that using dummy copy that looks like legitimate content is more harmful than using random latin. At least with real latin, you don't delude yourself into thinking that it's anything other than text used to decide formal typographic or layout choices.