I think most of these issues the article points out are somewhat short-sighted and superficial.
> They Use Classic ASP
I'm not sure they actually do, but even if that's true it's probably a choice they made in ancient times and they're sticking to it. And honestly, why not? It's not like we're dealing with a highly complex site that needs to be agile and extremely dynamic. They're probably just doing some light templating stuff and that's it.
> Script Tag Madness
That's a good point and it seems like an easy fix. However, most of these script tags seem to point to external vendors - most prominently Google - and that's probably why they're not messing with them.
> They Use Inline Styles
I agree it looks bad and it's also pretty easy to fix. On the other hand, those few extra bytes don't actually harm anyone. It's not pretty, but the argument that it makes the site hard to maintain is probably incorrect. I would think that no matter how many pages there are the number of actual templates used is quite small.
> They Use Ancient Float-Clearing Methods
Again, this is probably a hack from the dawn of time, and it seems to work. Would they do it the same way today? Probably not. But is it worth the hassle of taking it out for no reason other than pleasing nitpickers? Nah.
> They Use Tables for Layout / They Use <br> Tags Badly
Historically, for a while there that was an absolutely valid choice. Though I wouldn't write table-based layout code without cringing today, I have to take a stand here and assert that tables are not that bad of a tool. The standard argument that div/CSS-based table-like features are always better is somewhat hollow given the reality of actually dealing with the code. In practice, even CSS gurus do layout with HTML element structure all the time, they're just not open about it.
> They Have Duplicate Content
I'm not sure why Google doesn't filter these out. Not fixing that is somewhat of an atrocious move on W3Schools' part, but you can't really blame them for wanting the ad revenue.
> Their Embedded Code Examples are Ugly
That's true, they could do with an update. Syntax highlighting would be great.
> They Use Reflections / They Think “CSS3” is Part of “HTML5” / They Use the “keywords” Meta Tag
I don't care.
> Their Website is Not Responsive or Mobile-Friendly
Personally, I think that's a huge plus. I'm almost always annoyed when I get the mobile version of a site.