Absolutely. We can do this, and it gets us a little further. But the trouble is simple: it’s still static. Most – in fact, I daresay, a vast majority of – Markdown-based sites have one simple form of dynamic behavior: through links or menus, you can choose which of your many Markdown documents to view/edit. That is useful.
But TiddlyWiki does so much more. I can write a simple button that let’s me choose whether to include the simplified version or the more complete one of every tiddler on the page. I can perform calculations on the fly from a dynamic subset of my content tiddlers. I can change layouts with a keystroke. I haven’t had time to investigate the thread @Ste_W has created, but it looks from afar as though he’s creating spreadsheet like behavior just using TW’s features. Look at the work @Springer has done to help display content that is only implicitly present. Look at all the tools @EricShulman, @pmario, @saqimtiaz, @telumire, and so many others put out there.
I haven’t spent a great deal of time with any of them, but I’m pretty sure Obsidian, Joplin, Notion, log-seq, and all their ilk, have little of this flexibility. And if they do, it’s probably supplied through external plugin written by coders, not written with the same tools used for all other content by regular users.
There is plenty of use for such fairly static sites. I do a lot of documentation with Docsify, and have used Hugo and a gazillion other SSGs. I would love to be able to interoperate better with these. The work in this thread you’ve resurrected offers one promising start to that. But it will always be limited to a small subset of TW’s potential. I don’t see any way around that.