' A “D&D Compendium with Official Content”' - Rules have been available online for years. Check out www.d20srd.org for the most comprehensive set, but the "basic 5th edition" handbook is also available, and that's just the official resources. There's also half a ton of independently-run wikis.
' The ability to “Create, Browse, & Use Homebrew Content”' - Or, as those of us who've been on the web more than ten minutes call it, a wiki.
' The ability to “Manage Characters - Build, Progress, & Play”' - OK, this could be new. Well, really you could do that within a wiki, too. But it'd help to have a nice template, I guess.
' D&D News, Articles, Forums, & More' - You mean like WOTC has been maintaining for years?
' Anywhere, anytime, access on any device' - A website. That's nice. Why did nobody think of that before?