Okay, but is it not what you wished for, "a similar tool for the modern era"?
edit: I see I simul-posted with u/modeless, but I can't remove it now that there's a (duplicate) reply. Maybe mods can remove or at least collapse mine (their ID is one lower so they were first)
WinDbg is just a debugger: it does not assemble or disassemble. It can't patch running programs in memory. Moreover, I don't consider Windows to be part of the modern era, as I haven't used a Windows machine for 20 years.
So, no, WinDbg has nothing to do with debug.com.
Fun! So how was OP supposed to know your very personal and weird definition of what is part of the modern era?
If OP wanted to know whether WinDbg and debug.com can be considered feature-similar, they could have read my first comment [1], where I specifically said that debug.com is a "debugger, *assembler*, and *disassembler*". Of those three features, WinDbg provides one.
[1] https://news.ycombinator.com/item?id=48362927