Maybe roblox?
The other poster is probably right, the indie game scene is pretty prolific with jams and remixes and has more collaboration than most early web phenomena.
If anything, web development is far more arcane and challenging now. No one just writes HTML, CSS or JS in a text editor anymore, the bare minimum expectation is to use complex frontend frameworks and NPM and compile everything from other languages. Compared to the sprawling, byzantine nightmare of modern web development, JQuery plugins were a breeze.
I think, it's simply the case that the web has matured, and more people are concerned with content than the superficiality of quirky presentation nowadays. Just as it's possible for an author to publish a book without knowing typesetting or running their own press, one can publish to the internet without knowing even the basics of HTML, CSS or JS.
And of course the web has coalesced around a set of standard layouts and visual language, as any media paradigm inevitably does, mostly because it has done so around a few standard frameworks. But then let's be honest, most Geocities sites kind of looked the same, too.
See, the thing about all the modern development infra we have is that it wasn’t just invented for fun - it solves real problems. Jquery was created to smooth over browser inconsistencies. Webpack was made so that when you import 20 JS files they don’t all clobber each other’s namespaces (ok, there’s a bit more to it, but bear with me here). NPM was made so that you can install dependencies without having to hunt down the JS download on Google.
This whole thing of looking at the past with rose colored glasses is a bit too easy to take too far.
And then you have compile-to-js languages like Typescript, and the entire paradigm of "javascript as bytecode" which, for all of their benefits in adding safety, also added exponential complexity. Frontend frameworks with their own unique paradigms that generate HTML and CSS entirely in JS, and ignore the separation of concerns the web is actually built around.
All of these have their place and their value, but the fact that "vanilla JS" is coming back as a trend might be a sign that things have strayed a bit too far in the wrong direction.
Back in 1995, a web page was an experimental medium, with very few experts in the field, and few businesses seeing it as a key asset. It could took long to develop, it could look fancy and whimsical, and there were few other sites to compare to, with the same properties. The chance for a web user to encounter something unusual was higher, because there was very little properly usual yet.
Today the web is the main medium, with a lot of standardization which comes from the need to be readable, accessible, look clean, and take as short to develop as possible. The consumer expects the same: simple, familiar packaging, easy access to the content which is usually a piece of text or a picture. This leaves especially little room for fancy on small-screen mobile devices. The web is not more of a place for artistic expression than newspapers were in 1970. Whimsical and fancy designs exist, but they are relatively rare and special-purpose, promo or art pages.
But it doesn't have to be this way. Look at https://play.date/ or https://tokio.rs/, functional yet interesting. Tokio.rs in particular has the best implementation of one of the worst patterns in the modern web: sticky content that changes when you scroll. It's a great visual aid in this case, but becomes annoying quickly when overused.