There's still a decent amount of +0 groups out there from what I've seen.The quest design forcing you specifically into Mythic0 for a lot of stuff is idiotic. First, unless there's a World Quest driving a lot of players to that specific tier, there's little reward or motivation for anyone to play Mythic0. Unless you're a tank or healer you're going to have an easier time getting into Mythic+ runs versus being able to land a spot in the infrequent Mythic0 runs. These quests should be completable in Mythic+, some of them are and automatically award you the geegaw, but many aren't. All of these dungeons quests should be completely via Mythic+ or Heroic dungeons in the finder. Mythic0 runs can be like fucking unicorns. You have to wait for WQ's or just keep skimming custom groups and luck out.
It's terrible design.
What you can do is in the group finder search "c)" without the quotations. For whatever reason c) is a filter that brings up all the base mythic groups currently up. Saw that on Reddit a few months ago and I'm still not sure exactly why that's a +0 filter but it works great.