Except just needing HTML, CSS, and JS was never true. Back in 1995, JS and CSS didn't exist. But Perl did, which is what most cgi-bin scripts were written in. Then you had to learn mod_perl after you figured out Apache's crazy non-regular config file format. (Are you markup or not?! Pick a lane!).
Build scripts? LOL! Learn FTP sucka, and copy those files manually.
Wait… now I'm on a Windows server? What in the hell is ISAPI?
Now you want to send an email from that contact form on your site? Better learn how to set up sendmail servers. (WTF is m4? I need a macro language to generate the config file for my email server?!)
document.write("Hello World!");
Fast forward to 2004. Firefox (or was it Phoenix?) is hoping to slowly wrench dominance away from IE, but for now frontend devs gotta know ActiveX (insecure), Java applets (slow as molasses), and Macromedia Flash (you've got a DSL connection, right?). Don't forget JS has competition in VBScript. And oh, those .htc behavior files. All the old and table-based layouts are passé, and folks are demanding they be rewritten in that cool CSS now that Netscape 4 usage is officially dead. Still gotta fit those PDFs in sometimes though.
HTML is looking drab compared to that XML hotness. Better get on board with XHTML! Scratch that! All the XML flavors: XSLT, XSL:FO, SOAP, XML Schema (or RelaxNG for the cool kids), XPath, SAX, X-Force! (Okay, maybe not that last one.)
Firefox is getting better so much faster than IE, so don't forget to polyfill all the things.
Jump to 2010. We've got more browser engines than we know what to do with and they all render differently. Maybe not a lot in this one case, but different enough. Bring on the JSON! The rise of JS libraries brings us the choices of Prototype (the OG, but already obsolete), YUI, Jquery, and a new entry every month at least. Tree shaking? CI/CD? What crazy talk are you spouting now? I'm just barely handling minification and manual image optimization.
-----
Thank [deity] things today aren't as complex as they were back then!
To quote BSG: "This has all happened before. And it will happen again."