A web-based "Minecraft" has great potential, in my opinion, and has long been a dream of mine. My humble attempt at such a project: https://satoshinm.github.io/NetCraft/ (2017) - a port of Michael Fogleman's Craft, a simple Minecraft clone written in C, ported to the web using WebAssembly and Emscripten. It works, reasonably well (after a few small enhancements/fixes to Emscripten) but did not get very far. But it could be so much more, a "metaverse", if you will.
Minetest is a much more sophisticated application: paradust7's minetest-wasm port, even in its early stages, is already quite impressive. If it can be optimized, with streamlined add-on installation, seamless multiplayer/networking support, browser compatibility improved - I would not be surprised if this project catches on and gives Minecraft a run for its money.
Having the ability to easily casually play within a web browser, no install needed, is a massive advantage over the Java or C++ implementations of Minecraft - which have not (officially) embraced modding to the extent Minetest has. If successful, this project could capture the large and diverse community of Minecraft modders - able to more seamlessly deliver their creative content through the web. Excited to see how it develops further.