Geocities sites were not some special dark corner of the internet they were representative examples of the extant design of the era.
In the modern web, pages are still in HTML, font's can still be adjusted, and ads are automatically filtered out.
Huh? I remember loads and loads of pop ups
Ah, yes: Java applets that made your system crawl.
Flash interfaces that likely 'worked', but had been designed by an alien with no comprehension of human cognition or interface design.
Text that was delivered as a set of lossy JPEGs because the designer really, really wanted a font that was only installed on a dozen people's computers. (Good luck accessing that if you were blind or, more likely, stuck behind a slow, unreliable dial-up connection.)
Pop-up ads your browser was too stupid to block.
Endlessly looping MIDI making you forever hate Skye Boat Song and The Entertainer.
Good times, good times.
How is bad interface design a problem specific to Flash? Surely you can create a bad interface with modern tools just as easily?
With HTML you at least have a stronger pressure to use the same text boxes everyone else does, for example: There's more standardization of basic building blocks. You can go whole-hog with reinventing the square wheel only this time making it diamond-shaped and made out of cream cheese, but it's harder.
In Flash, apparently, there's less of a counterbalance to going off entirely on your own and making something only you can understand.
And the rise of AJAX and client side javascript web applications and made the web much better. Gmail was one of the first "ajax" applications that got big./