Crucible is probably my favorite mode in Destiny. Do I need TTK in order to continue playing it, or am I SoL?

From Bungie's TTK Release Notes:

Crucible
Year Two Crucible is now in effect (Requires the Taken King):
Rift, Control, Clash, Skirmish, Salvage, Rumble, Elimination are now Year Two core playlists
When Trials of Osiris is active, Elimination will only be playable via Trials of Osiris >playlist
Featured Daily and Weekly activities are now active
Year One Core Playlists now contains Classic 6v6, Classic 3v3 and Classic FFA playlists

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It does look like you're options are pretty limited, but you can still play!