Standing outside Thomas Richards' hideout in Windrose with only a "Leave" dialogue option is the most common roadblock players hit during The Bitter Pill. The door is gated by a separate prerequisite, not by clearing the surrounding island, which is why wiping every pirate on land still doesn't open it.
Why the door won't open
Richards' hideout uses a key-item check tied to the main story, not a kill counter. The outer camp can be fully cleared, and you will still only see the option to walk away. The interior door requires you to present four Black Marks, which are quest items collected during the main mission "Revenge is Best Served Cold."
If that main quest hasn't been started or progressed to the Black Marks stage, the prompt simply won't appear, even with a clean island.
How to collect the four Black Marks
Step 1: Make the Coastal Jungle your active region. Set "Revenge is Best Served Cold" as your tracked quest so the Black Mark chest markers display on the map and compass. The Bitter Pill marker alone won't point you at the chests.
Step 2: Sail southwest from Doctor Galen toward the Coastal Jungle. Expect Blackbeard Gunboats patrolling the route. Pull them one at a time rather than sailing into a group, since taking heavy hull damage here often forces a return trip before you even land.
Step 3: Open each marked chest and confirm a Black Mark is added to your inventory. There are four total. Missing one is the most frequent reason the hideout door still won't open later.
Step 4: With all four in hand, sail further southwest to Richards' hideout. Approach the main entrance, interact with it, and select "Show Black Marks." The door opens, and you transition into the camp interior.
If you still see only "Leave"
If the dialogue prompt is still missing the entry option, run through this short check before assuming a bug.
How to confirm it worked
You'll know the gate check passed when interacting with the entrance shows "Show Black Marks" and selecting it loads you into the inner camp area. The Bitter Pill objective then advances from "Infiltrate Richards' camp" to searching the camp, where Francois Arnaud's Letter is found in a chest past Richards' room. From there, the quest continues to the gunpowder crates at the Blackbeard Ruins Excavation Site and on to Tortuga.
If the door interaction still fails after confirming four Black Marks and an active Bitter Pill quest, that points to a save state issue rather than missing requirements. Reloading or relogging has resolved similar boarding and trigger hiccups elsewhere in Windrose during its current Early Access build, so it's a reasonable last step before reporting it as a bug.