That could be happening because of your wifi quality, PC Specs, or browser. if you have more than one network or more than one router, try switching to that, but before you try that, try to switch browsers to something like Chrome if you aren't using it.
I've been having a similar problem with other games that open a Unity WebGL window and stops loading at 90%, and I'm on a top-end setup. I'm wondering if it's a bug on the devs' end, or some network setting/firewall preventing something. In any case, it is also an indie game on Itch, most of which don't run well (if they run at all) because they're not optimized whatsoever, but I can't say for sure on this one as I'm also having the same 25% problem.